[smileybarry]

It could also just pretend to encrypt your drive with a null key and not do anything, either.

You need some implicit trust in a system to use it. And at worst, you can probably reverse engineer the (unencrypted) BitLocker metadata that preboot authentication reads.

[lazide]

No, that would be trivial to verify with any other operating system.

Key ring contents (and what is done with them) are typically much harder to verify as they’re encrypted.