Grass is baked in editor, so as not to need ticks.
Ofc, if you are in editor, then the grass and even foliage have something - which I would really hope is controlled by the landscape for performance sake - that would alter their position as you sculpt.
Even considering that, tick?
Someone was smoking crack when they set that up.
Sculpting is an input driven action. You already have the interaction needed to make changes without having to run checks on tick.
And it pretty much goes for any and all actions you can take on the landscape, including the nondestructive layer sculpt stuff.
You can probably take it as a brilliant example of just how bad things are all over the engine when it comes to performance…
Landscape is trash that no professional would ever use. So, obviously it’s a given that it is fully unoptimized and worthless.
But you’ll likely find the same overlooks (or flat out compromises) all around other key systems, including sky athmosphere, volumetric fog, chaos, etc…
And all those parts are not supposed to be Beta…
So imagine stuff like Nanite and Lumen?