There are some things that have always been off to me about this.
First would be the vertical block which was installed in modern times. On G1 and G2 there can be seen several vertical blocks which according to Jon Bodsworth were repairs carried out by the Egyptian Army if I recall in the 1960's. This vertical block being a modern repair at least is confirmed by Hawass:
Quote
The surface of the east side of the Pyramid of Khufu was once covered with stone rubble and sand. Jean-Philippe Laure and Abdel-Salam Hussein were among those who cleared the surface of the east side.
After this process was completed, all the stones were shown clearly and it could be noticed that there were fragile stones on the east and south side of the pyramid. Among these fragile stones, were the four pieces that flanked the vertical big stone that were highlighted by the infrared thermography analysis shown at the press conference.
The modern restorer placed this vertical stone to support the four fragile stones and used cement in the restoration. Anyone can see that this stone is not similar to the stones used in the construction of the Great Pyramid. We know that all the stones for the building came from quarries on the Giza Plateau, and the location of the quarry that provided the building material was to the south of the Pyramid and to the east of Khafre’s Pyramid.
[Emphasis mine.]
What can be clearly seen is that the core blocks in this area were hacked away at some point in time, maybe even modern times, to further reveal this space. Laure and Hussein after clearing this area would have seen this for what it was before it was repaired in modern times as would the countless others who studied G1 between the time this was revealed and when it was repaired, perhaps decades later. Back to this in a minute*.
To continue with Hawass:
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The restorers at the Giza Plateau used cement in the restoration of the vertical stone and it is easy to distinguish between the modern and ancient mortar. Mamdouh Eldamaty said at the conference that a passage had been cut in the rock located directly in front of the three stones, but this is not a passage or a tunnel. Rather, it is a natural crack in the rock that can be seen by the naked eye.
There is another important point that many people do not know about. The base of the Great Pyramid is cut some eight metres into the rock, and this can be seen clearly on the south side of the pyramid. It would be impossible to see a room or tunnel in this location near to the rock.
If this room exists, it would have to have a function, and since this is not the case the claim cannot be valid.
According to Hawass this "anomaly" is a natural crack in the bedrock which he says can actually be seen with the naked eye.
* When this was uncovered by Laure and Hussein, decades before modern repairs, it would have been obvious to them and to the countless others that something was different about this area. If there was something actually there someone would have at least made note of it before modern repairs were made. There would be no politics in the early/mid 20th century from stopping anyone who saw it from digging right in and seeing if anything was there which if something was there of interest it would have made their career. And given no one has ever said a word of it, apparently, nothing was found.
Lets look again at the thermal anomaly:
The hot spot is the horizontal blocks to the right of vertical block (and a little to the left) and a long vertical block next to those and the two supporting blocks of the vertical block, and another shorter vertical block to the right of that with core block sitting on top. See here paying attention to the two vertical "blocks" to the center right:
I had a better picture showing the joint of these two "blocks" that I can't find again, but look here at 0:15. and again at 0:29. The rub is that there is no joint-its one block. The "front" has the appearance of being cut to the height of the first course and the "back" is cut to the height of the second. And if you look here:
LARGE
The supposed "core block" above the shorter vertical "block" is actually part of the long vertical "block" behind it and by default the shorter vertical block below it. These 3 "blocks" are not individual blocks at all, but one mass.
I can't find a clear picture of the apron blocks (paving stones), but this here:
Seems to show that the apron blocks leading up to the long vertical section appears to "stop short" giving the impression this "block" sits below and behind it with some kind of "filler" in between. All things considered it appears to me this whole section is actually bedrock, part of the hill G1 was built on, that Hawass says a fissure of natural bedrock can be seen apparently behind it, that was carved like other sections that can be seen at G1 like here:
So what are we looking at here-if this is a chamber then this area would be the "door" except there is no lintel, jamb, or frame. Instead it was stuffed with relatively smaller horizontal blocks in ancient times directly next to a large section of cut bedrock/hill which also extends behind this whole section. This area when revealed in the early/mid 20th century in which it discovers and/or those that came after would have had no compunction about removing these blocks to see if there was something behind it which would have made their careers. But instead they just ignored it and left it be only to be fixed up decades later by the Egyptian ACE.
I have a different scenario-there is no "chamber" and this "anomaly" is exactly what Hawass says it is. This is an area cut from the hill which the section the horizontal blocks are now located (and behind it) became unstable at some point during or sometime after construction requiring repairs which is exactly what these horizontal blocks look like and not to hide some "secret chamber". These "hotspots", that all happen to be concentrated right in this area, are just a void created from deteriorating fissures of the bedrock hill of which these vertical "blocks" and "core block" I have noted are carved from.