They do have a copy of your Bitlocker key if you are dumb enough to allow it to sync with your Microsoft account, you know, “for convenience.”

Which I don’t believe is the only way it can leak. It’s well known Microsoft can access anything and everything on an internet connected Windows PC whether there’s a Microsoft account or not. If the nazi’s push for the device of someone on a local account only, you know they’ll magically find a way.