No, Seth's cursed wish on Anubis' growth wouldn't stay anyway because it feeds off of Anubis' own lingering wish to make his "father" happy, so if the one Anubis believes to be his father changes (if that is no longer Seth) then Seth's cursed wish can't continue to feed off of Anubis' own wishes as much as it did before the reveal, and thus the curse wavers.
The *other* curse, though (the one on Anubis' arm, which is a different, separate one) may on the contrary be getting worse because the shattered human souls that made that curse are no longer half-appeased now that they found out that the one they're killing isn't even their murderer' real son, after all (so now those souls might be more furious than they were before, when they thought that at least they'd be getting the chance to get back at their murderer by harming his child, at the very least).
thank u ヾ(☆▽☆)
can someone explain everything up til now i really dont understand at this point like wasn't real Nephthys inside the mirror amd seth already know that anu wasnt his son and cursed him so now curse should stay anyway right