This suggests the checksum is used to identify whether the binary is known to BOT, and thus whether BOT can optimize the binary.

I do wonder what this "optimize" step actually entails; does it just replace the binary with one that Intel themselves carefully decompiled and then hand-optimised? If it's a general "decompile-analyse-optimise-recompile" (perhaps something similar to what the https://en.wikipedia.org/wiki/Transmeta_Crusoe does), why restrict it?