Absolutely not.
If you don't subscribe to the idea that a smaller fighter can a) lose a very close fight to a much bigger guy, and b) maintain his P4P spot, then you essentially delegitimize the concept of P4P in the first place.
This wasn't a situation where the bigger guy blew the doors off the smaller guy, so you could theoretically still argue that he was bigger AND better (see GSP vs. Penn 2).
The difference between their sizes tonight was larger than the difference in their effectiveness and performance.