Encryption on Replaced SSD

Had a 2017 iMac that had a cracked screen. Decided to get a Late 2014 Mac Mini to get by for a while. Took the 500GB SSD (running Big Sur) out of the iMac and installed it in the Mac Mini over the weekend. Everything is running well, but I noticed when I was checking settings in Privacy/Security that FileVault was not turned on. Thought that was strange since it was turned on when the SSD was in the iMac.

Question, is FileVault specific to theOS install on the SSD, or is it specific to the machine the SSD is installed in?