It's based on EPV, another horse dung stat championed by the worldwide leader in sports horse dung and the article is from the leaders in abusing horse dung stats. Now there's a helluva combo...if you're making fertilizer
I don't advocate doing it as a primary means to move the chains. I advocate playing conservatively and mixing it in unpredictably. It primarily works because it is unpredictable, IMO. Nothing scientific about my opinion though.
Absolutely. It also doesn't take into account any number of other contextual items that would potentially make a huge difference in the outcome. That's one of the reasons 538 is basically useless.