they'll sell you the "hardware limitation" bull****, for sure. the reality? chances are its just....MARKETING
you see? glance can really be limited by hardware, that's a fact. but alot of phones don't have it due to marketing strategies and extracosts(which i dont think they are so much, what? 5 extra bucks for iterating it from other phones?)
let's look in 5xx family. 520 has it, 530 nope (but no surprise, since that phone is a flop), then 535 arrived without it too...ok, hardware limitation. then...532 has it. but there is no way 532 to literally have a better display than 535. i bet it has the same display just smaller.