Re: This, because we can't overwrite files that are in use.
It may be a terrible oversight but it may also have no remedy. It possible that disabling bitlocker is required because the actual upgrade is performed in WinPE (that can't get the key from TPM) or maybe because major changes to the system can result in bitlocker lockout (where manual entry of the key is required). So Windows suspends the BL for the upgrade and resumes it after next boot to Windows (since 8 it's SOP anyway) when new system can re-establish trust with TPM (and prevent lockout at the next reboot). Just a guess, but I'm curious if the same process would take place in SP1 update to Windows 7 and 8.1 upgrade from 8.
Biting the hand that feeds IT
