The exploit is really easy to pull off, you can crouch underground in a 1 hole space so your head pops through the ground and that gives you basically admin vision underground, other ways include using a hatch to lift your character up so their head goes through etc. This also works for things like turrets, which lets them fire through the ground and hit anything within range, so they can kill players without players even knowing from where etc.
You can even take it a step further and use a door to clip your entire player through the ground and that gives you the same advantage. You can basically kill players nearby that are on top of or underground and is a really terrible exploit that I've seen on just about every single server that I've attempted to play on and sadly, it has nothing to do with client/server lag and is just a flaw with how they have it implemented.
But still, when it comes to raiding, being able to just tunnel around or beneath defenses and collapse whatever you want hurts raiding (IMO). That's where this idea is born from as I've seen this sort of idea implemented in other games and it worked really well.