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 Bitloc…
One can easily obtain the recovery key on a system by doing "manage-bde -protectors -get c:" in an admin command prompt. This is not a vulnerability, it is by design.