my understanding is that the owner of the flame system can do whatever they want with it and so renting it out is fine.
staying on support is the owner’s problem, and if they drop off support they’re likely to rent their system out less.
every rental machine I’ve seen has been completely wiped before it came into whatever facility I was at, and I personally wipe any rental machines before they go back. If sensitive material floats from one facility to another on a flame nobody bothered to wipe, someone’s going to be in some hot water.