Well, I mean, Golden State is widely regarded as the best team since the '96 Bulls.. so I'd think so.
Also, if he'd said "a crappy team wins it half the time", you'd have a sterling rebuttal on your hands. As it is, you're just going on about the semantics of "best team". I'd agree that the term can be meaningless if there's a big cluster at the top ('08 for example), but I don't think that's usually the case.
Is there always a lock, indisputable number 1 team? No. But it's not rare, either. And his point could even hold by taking a small top tier that has separated itself as a single "best team". But going back, there have been clear, unambiguous best teams for most/all of the season - (winners in bold)
Kentucky in '15 (yes, Duke, Wisc, and healthy VA were elite, but not on the same level)
Florida in '14,
UL or IU in '13
Kentucky (or healthy UNC) in '12,
Ohio State in '11
UK or Kansas in '10,
UNC in '09,
A bunch in '08 (really weird year - 4 1 seeds at the top - I don't think there was a clear "best team", but you could argue Kansas was it? Maybe Memphis?_
Florida in '07
Duke in '06
UNC and Illinois in '05
UCONN in '04
Arizona in '03
Duke in '02
etc