I see no reason why we wouldn't see more wear in one half of the chain than in the other half if there were really an advantage to be gained by regular cleaning. The wear is on the individual parts of each link so if there's a benefit from cleaning that link it should show up as reduced elongation of that part of the chain.

It's the other 'studies' that I don't trust where someone starts a rigorous cleaning procedure and then reports a somewhat greater chain life. But if you know you're trying to keep the chain really clean won't you be just a bit less likely to go out on a ride in inclement weather, avoid routes with dirt/gravel sections, or do a myriad other things that may increase the life of the chain? Never trust studies where they haven't taken care to keep all the other variables fixed.