[2020] Why no filter for non-booster cards?

With June’s updates to collection and deck builder, and a new explicit list of all the commands you can use to search, why not add the much-requested ability to filter out cards not found in boosters? Figuring out if you’ve collected all of M20 and ELD and THB is a huge chore thanks to the M20 welcome deck cards and the ELD brawl cards and the THB Whatever deck cards. Plus there’s things like the early promos (Ghalta, ral, vraksa, teferi, duress, Firemind’s, etc) that all really should be styles, but failing that, at least shouldn’t make you think you don’t own 4 of that card when searching q<4.

This has repeatedly been asked for, but I’ve never see a wotc response. Is it on a list somewhere? Has it been forbidden for some reason? Is it technically harder than it seems like it’d be? (Seems pretty easy) I’d just really like to know so we can stop asking.