Larian wants Facing to be a thing because it was such a huge mechanic in DoS 2. So they are hamfisting it into the rules of 5e, even though it isn't supposed to be (outside of a sort of variant rule in the DMG which no one uses). WotC has explicitly stated that enemies are aware of things around them once combat starts, absent some other effect (Blindness, Darkness, etc).
Which is to say, enemies shouldn't have sight *cones* in combat, they should have sight *circles*. So defo agreed there.
More over, Stealth should require an Action, unless a class feature otherwise changes that. But again, Larian despises restricting gameplay abilities to specific classes and wants more Swiss Army Knife characters that can do everything, so not holding out hope for this change.