Don't know by own experience if the Sitech solution is good or not, but what I heard from buddy's is that it can be restricting while doing a valve drill. It depends on your body build it seems if it's restricting.
It is quite common to run into this comment in the forums. Any poorly fitting dysuit can be restrictive while doing a valve drill, true.
But I'd guess it is more about the fit altogether, because a properly fitting drysuit with a quickneck ring doesn't restrict valve drills or anything else at all. Heck, I have never even noticed the neck ring when underwater. (it does feel a bit uncomfortable when walking wth heavy rig).
Maybe retrofitted quicknecks are causing problems to overall drysuit fit in the upper torso area? Or maybe I just had a very good luck with my Santi.