I believe these are some properties. 5D3 behaves the same, it refuses everything outside Canon range.
The routine from Expo menu simply tries them all, until one succeeds.
Edit: on 5D3 it seems to be 80040033, uint8_t data[4] = (uint8_t*)buf; data[0] is max iso, data[1] is min iso, data[2] is 1 with isos astronomicos, 0 with normal ones.