The UESP tends to get a lot of the summeries wrong. A lot of the time, it's someones opinion. Another half of the time they get an in-universe perspective as fact. They are (or at least used to be) pages that insist the Tribunal and Dagoth Ur turned evil because the Heart of Lorkhan was "evil."
Personally, for me, what is wrong with the UESP is that it is one or two persons their opinion.
It really is quite hard and you have to cite and argue quite vehemently to get anything changed.
Now, that is often not a bad thing.
However, I find that the regular 'anyone can participate' concept of a wiki does trump over things like the UESP when it comes to new things, simply because of this structure.
I also have, personally, a bit of trouble with things they declare as 'canon fact', while I argue there is no such thing in TES, meanwhile Im no editor there and things I, personally, find to be unsubstantiated or ambiguous stand there as 'canon fact'