I can only report on what I've read from some owners on this forum as I don't have the system on my toyhauler.
I've always felt the way you do: the 6 point system should be solid as the proverbial rock. But I've read quite a few posts from people with the 4 point and 6 point level up systems that say they still get a fair amount of trailer motion from movement inside the trailer. Some have installed something like the JT Strongarms and Roto-Choks, or a 5th wheel tripod. But it does seem that a certain amount of movement is the norm, and it depends on the individual as to how much is too much.
I'll be watching this thread because I'm curious to see if old posts are borne out by new ones.