Not sure if the team is already aware of this but I might be able to shed some light on the extent of it.
Firstly Roar and some other phazing moves/methods are usable on Dynamaxed Pokemon, which is verifiably not true on cart (thanks duckpond for the easy to google video).
https://replay.pokemonshowdown.com/gen8ou-1012756689
Additionally, as a consequence of phazing a dynamaxed pokemon, the now phazed Pokemon keeps its 200% HP bar for the rest of the match (as far as I can tell).
Evidenced here with Red Card:
https://replay.pokemonshowdown.com/gen8ou-1012756689
and here with Dragon Tail:
No evidence but I also noticed that Charizard had 596 HP after being Roared in the first replay as well.
This may be a non-issue if Dynamax users can't be phazed on cart altogether, but it's worth noting if that is not the case.
Disguise has been nerfed on cart to deal some damage in SwoSh IIRC, so this is likely working as intended.