It doesn't fundamentally solve anything. You want to be able to identify a specific person or at least a relatively expensive device so that if you ban them they stay banned.

Private access tokens are also a repackaged WEI as far as I'm concerned.

The article mentions that they use Private Access Tokens on iOS, so I'm not sure where you're getting the idea that they're "not adopting" them from

"pretended" ... do they even care any more?

Not Invented Here Syndrome?