The point is that Politifact could be the most accurate source the world has ever known (HAHAHAHAHAHAAHAHAHAHAAHA) but that doesn't mean their data can't be manipulated.
What if they actively choose to only Factcheck lies by Trump and only post truths by Democrats? They could have 100 fact checks of both Joe Biden and Trump but purposefully toss out any lies by Biden and toss out any truths by Trump to make it look like Trump is a bigger liar Biden. Sure they'll throw in a few truths by Trump to make it not so obvious, but it's obvious to anyone with 2 brain cells to rub together how they can easily manipulate the data in such a way.
And hey look at that, that's exactly what they do!