The concept is great (fabric, foldable, magnet mounted) but in practice the magnets are not strong enough and the flimsy fabric\construction just flops around too much.
First off,I don't have a Vision and I don't use my phone for FPV,BUT I do use the anti glare screen protectors on my phone and they work fairly well although not completely infallible.
One thing I've noticed is very small print and similarly small details do become slightly grainy or distorted by the anti glare film.I don't think it would be too much to still use them for FPV applications though.
They're pretty cheap to buy so worth a try.