there’s more reason to put glass screen protector on the mini LED iPad than ’regular’ ipads.
i’ve been using glass screen protectors on my devices for couple years now, not that i dont have AppleCare or what, but just i love my devices being PERFECT, SPOTLESS. Sure i can use my applecare to replace my iPad/iphone every couple months, but certainly not as frequently enough, there’s still scratches. (BTW, I’m using sapphire on my iphone, absolutely perfect, except the price).
i have never notice any reduction in picture or display quality, the only downside is reflection. it’s a bit annoying during the bright days (but not as annoying as a tiny scratch). With much brighter mini LED, i expect this to be less of a problem on the new iPad Pro.