After a little consideration, I have another thought - and it may be quite insignificant, but here goes:
By moving the spanwise CP inboard (i.e. outward rotation) the outer wing panels work less hard, and thus the tip vortices are not as strong. Isn't this increased (equivalent) aspect ratio?
If so, and the climb performance is marginal, then outboard prop rotation might give some climb benefit.
Someone who's progressed beyond Aero 101 might let me know if I'm off-base here.
PS Thank you Brian for that excellent research!