I'm not an expert in this stuff, but that's one of two reasons why I don't like the prospect of integrated boots. Neoprene socks are much more flexible, whether wearing one or three sets of wool socks. Secondly, all the rubber boots seem to have weak points where they connect to the underlying neoprene (particularly the top-facing L of the foot). Enough repeated stretch and wear and you'll have to really finagle a fix or replace the entire boot. Neoprene socks are dead simple to fix, and you can just wear regular wet boots over em. Loads of flexibility.
Not to mention less need for gaiters.