Great explanation. Yes - I’ve done this before! Built up a system with a RAID array but then realized I wanted a different boot drive. Didn’t really want to wait for dual 15Tb arrays to rebuild - and luckily for me, I didn’t have to! Because the metadata is saved on the discs themselves. If I had to guess (I could be wrong though) - I believe ‘sudo mdadm —scan —examine’ should probably bring up some info about the discs, or something similar to that command.
~$2500USD/ea, for anyone else as curious as me