Honestly, I feel like the way these people play the pieces twice as slow isn't the bad part. Richter did it to an incredible effect in D 894. (I'd love to hear Schnabel play Op. 2 No. 2, and I play the Moonlight Sonata at about the tempo Winters plays it. There's a reason why many people do the thing where they play the fast movements extra fast and the slow movements extra slow - it's to prove both your technique and your expression.) It makes them different pieces in themselves, rather than fully skewing them. But I get the sense that they're using WBM "theory" as a way to back up their poor technique. (For example, he plays the Moonlight 1st movement at a reasonable, though sort of slow, tempo, then proceeds to an obvious outlier tempo of a 3rd movement.) I mean, come on people, if you can't stand the technique of Chopin etudes, why not just play a Schubert sonata? Don't attempt a virtuoso piece that has both zero technical or expressional value. (Expression is not slowness and sheet music dynamics. It is much more than that and cannot be expressed through words or mannerisms that may "trick" the viewer.) If you can do great expression, amazing. Play Schubert. If you're into virtuosity? Play Liszt. You can't just be like, oh, I can't do technique on a technical piece, so I'll just slow it down twice as much and *hope* no one will notice.
It's one of those things where something is so bad it's good.