Grounded Effect

I find the grounded effect a cool mechanic, it is not a strong cc imo, just stronger than slow maybe, but weaker than the other forms of cc. However, sometimes I think "oh, miasma will definitely stop this ability" but nope, I was playing cass against Xayah today and she could ult within my W, why can she ult in the miasma but Fizz cant troll pole there? imo, they are pretty similar abilities (Xayah can move while she throws her feather storm), also, Thresh lantern is a pull ability right? it serves as mobility, enemies cannot take Thresh lantern while standing on miasma, however, Jarvan can still EQ within the miasma, it is a pull ability aswell, so like, how dah heck am I supposed to know on what does the miasma works on and on what it does not? was this overlooked or does it work exactly as intended? Riot, are you gonna take a look at this or is it too unimportant? I think this kind of mechanic irregularity must be looked at cuz it really ruins some games.

Thank you for reading!