The problem is its the same on any difficulty, Difficulty does not stop auto-aggro volumes from rushing you second you walk in, it doesn't stop zombies from being behind things constantly. Its just getting stupid now. Especially the zombies in closets, hidden walls and even dropping down from the cieling, they make NO SENSE, like what the was a zombie doing in those places anyway? its completly immersion breaking and quite frankly just unfun. Office_04 in A20 exp is a prime example of a unfun poi. literally every single sleeper volume auto-aggros second you walk in, including zombies dropping from, the cieling/walls in almost every room. Whats worse is in the loot room one of the sleepers spawns right beside the place close enough to be hugging them, this sleeper doesn't spawn till you actually walk into the room, so its a 100% cheapshot as its right beside you when it spanws.
Like stealthing does save ammo when you can actually get a sneak attack which in A20 is kinda rare due to most sleeper volumes just knowing your there second you walk in and charging you. Stealth clearing is also much slower than just going in guns blazing, your trading speed for saftey. I've pretty much stopped investing in the sneak perks in A20 as they are of very little use anymore.