Recently I wiped the contents of the Trusted Platform Module of a laptop. Now the laptop failed to boot as the Bitlocker key was not stored in the TPM anymore.

To my surprise it was possible to get a code from Microsoft to access the laptop's disk again, as one of the admin accounts was a Microsoft account.

I strongly suspect, Microsoft does only activate Bitlocker during the OOBE if it can set-up this kind of Bitlocker recovery mechanism, storing an (indirect) decryption key at Microsoft.