Clearly they prefer their Vision Cones mini-game instead of the 5e system.
Rules of 5e just state: "You can't hide from a creature that can see you clearly." Creature seeing you clearly or not is usually determined by DM and requires his own judgement. The DM's role is reinforced by: "The DM decides when circumstances are appropriate for hiding." Thus, Vision Cones are not infringement upon 5e rules, they are an attempt to simulate DMs ruling. We might agree, that Larian's vision cones are too generous, but shouting "Follow 5e" is not a valid feedback or concern in this case.
The spirit of the D&D system is that the Stealth skill is actually used to determine the success of sneaking, and not some 3rd party system stacked on top that completely overrides it. So let's not start rules lawyering here.
And reading that first sentence literally and allowing players to hide in melee range during turn based combat is clearly asinine DM'ing.
Interesting take, since the first sentence literally says you can't do that, if they can see you. If they can't see you, range doesn't matter. In fact, I'd argue that, if they can't see you, then sneak wouldn't even be necessary for a sneak attack, for example, since being undetected, they can't see you, would give you advantage.
