I think the the Boot Manager can end up on any drive depending what you had connected when you installed Windows.
If you only had 1 drive connected then the Boot Manager and the operating system will both be put on it.
If you have 2 or more drives connected then the Boot Manager may end up on a different drive than the operating system.
That's my understanding and why, especially with SSD's, it's recommended that the only drive that's connected when installing the operating system is the boot drive.