As far as I am aware these "agro volumes" actually have some specific trigger point. For example, in Red Mesa one of the trigger points is the few tiles in the corridor leading to the doorway of the loot room waking up all the sleepers around the corner.
So the "correct" way of doing the Red Mesa is, apparently, going to the bunker tower, doing the hole into the wall of it and then shooting all the sleepers in the head through that hole and they will not wake up even if you step into the corridor they are sleeping in. You can even sneak right past them until you hit the trigger in front of that loot door doorway.
The "aggro room" does not really provide suspense and excitement, in my opinion. It just specifically targets a "stealth gameplay" approach, but you learn these after the first three times getting raped and after that they are just there to ensure that a player just cheeses the POI by strategically avoiding the trigger tiles (by going, for example, through walls in key locations instead of using doorways). What these are, basically, are the trash-in-the-doorway but with NO VISUAL CUE THAT THEY ARE THERE and no proper way to do something to avoid these, because I consider it personally a form of "cheating" to go through a wall because I have a meta-game information that this particular patch of thin air in that doorway or entrance is a trigger. My character should not know that, but I do.
The next level of "screw you", I have observed is, ofcourse, the scenario where the POI spawns the zeds at you from thin air. But I am not sure if this is somekind of a bug or is this the next level answer of to the POI designers to the players "cheesing" the room by going through a wall and killing their precious "surprise" sleepers before going through the sleeper volume trigger. Cant kill what is not there, after all, until you are served a dish of dozen ferals rushing you out of thin air. I am hoping that this is some kind of bug. But considering what I have observed in regards of POI design I would not put it past the devs for it to be deliberate. But if it is deliberate, then, please, at least have the decency of spawning the zeds few rooms away out of my direct sight, at least. Will not help in multiplayer as there could always be a player present to observe spawning of them, but at least when solo it would not be as immersion-breaking, maybe.