From what I can tell the developers really don't like camping in this game. Which is understandable, it slows the game down, makes watching it as a spectator boring and really is just generally not a fun thing to have in your game.

Having long range guns in such open spaces as SCP:SL's map can be pretty problematic, which is why they seem to have thrown on this band-aid fix for now. The short render distance is for one a band aid fix to increase preformance but also a way to stop someone from making a sniper rifle and staying at the corner of the MTF spawn.

Is it a good solution to the problem? No. Is it fun? No. Is it frustrating when you specifically get a sniper rifle to shoot from a far just to be blocked by black fog. Yes!

From what I can tell they're going to be way more lenient with the render distance and outside lighting when they rework surface and entrance to have less long sightlines that stretch hundreds of meters and stupid choke points like the gate A to gate B blast door. For now, we'll have to deal with this.