When I search "Aqua Flush V" I get "Aqua Magic V" - which is right?
We have an Aqua Magic IV, and on that one, the blade seal is as OP describes. It runs across the bottom of a Seal, not between two layers of a Seal like most other Thetford toilets. If the AM-V works like the AM-IV, then there's no groove in the Seal to be cleaned out. The AM-IV parts list shows this. The AM-V list does not, so I can't confirm Thetford used the same design.
AM-IV, now AM-V, is the cheapest of the cheap. Bottom of the line. I'm amazed that our 15-YOA one still works as well as it does. I can leave water in the bowl and it stays for at least several hours.