I think they are talking about any altered data. But realistically, combining resource consumption and detectability, they are presently only bringing the hammer down on super obvious stuff. Whether they decide to push forward, is something only they themselves would know for sure.
Well, it's kinda easy to find (if they decide to look for it). It's basically a mon with a species ID that isn't available in SWSH.
Also, being in nursery isn't safe; they fixed Alolan mons with invalid moves (due to GO->HOME move transfer nonsense) anywhere in the save, even in nursery. They can see every aspect of your save, if they really wanted to.