I've looked at KB articles and the like, and I can't even find a
reference to a situation where the BIOS only supports 32-bit LBA, but
that Windows can detect the full size.

I guess it comes down to whether or not Windows cares about the
translated geometry that BIOS gives it.. seems like it is disregarding
what BIOS reports since it can see and access the whole drive. At least
I think that's the case... wish I could find a straight answer though!