Yes, I agree that since MOV is a container, we can say that WMP handles MOV just fine (as PaoloM pointed out) and that, since it can contain media encoded with arbitrary codecs, expecting WMP to be able to play any possible MOV file simply does not make sense.
While this is technically correct, I would propose a more pragmatic approach: the QuickTime format can require arbitrary codecs, but the QuickTime player comes with a well-defined set of codecs out of the box. So, IMHO, a possible benchmark would be that WMP handles MOV reasonably well the day it achieves parity with QT without add-ons.
I don't know if this makes sense to you...