https://www.reddit.com/r/math/comments/19fg9rx/some_perspect...
The tldr is that a lot of the heavy lifting was done by an algorithm used called Deductive Database + Algebraic Relations.
I must stress that the results were still impressive, at the time scoring a silver in Olympiad Geometry was seen as something out of reach for AI, and it's impressive that they were able to do this with a mostly deterministic approach. The point is that you really didn't need that much AI to actually score a silver.
Let me make sure I understood this correctly. Author from reddit formed his opinion based on "examining the Nature article more carefully"?
The above explanation on page 5 was really interesting to me - so it's not that AlphaGeometry2 failed on these 12% of problems, but rather that it literally didn't have the words to tackle them.