The plates I have seen were screwed on. I am not sure I would want one that was held on by the rounds themselves. They have to fit well, else the brass can bulge into the crack, but the only person I actually knew who used one said it worked fine.
I understand those plates are used mainly by folks like my Anglophile friend who want to fire the original ammo. For practical purposes, the .45 Auto Rim is better, but it also needs loaded down.
Re-reading my post above, I note some possible confusion. When I mentioned trimming the rim on .45 AR, I was thinking of making .455 brass for an UNshaved cylinder. But the technique will work also for a revolver with a cylinder that has not been shaved quite enough.