This seems a good research item ( and a potential change to new model pre/pro) as it relates to the 950's processing. And while I agree that many speaker set ups do not involve full range/large speakers across the front (or surrounds) there is always the possibility of doing so. For example Def Tech speakers with powered subs in them would include the L/R fronts and the centers for a lot of their speakers.
My experience with my 950 is that I have to set these speakers (L/C/R) to small to get any signal to the sub. Which is not alwyas desirable since I could run full to the 3 fronts since they have 8" powered subs in all.
I think that the 950 limits this ability. It's either set to Small to get LFE routed to sub or its Large and then there is no sub to be selected when you calibrate.