[endx7]

sometimes, it depends on whether you had the pet before the PetJournal merge.

If you had the pet before, DismissCompanion works. If you obtained it after, whether it was captured in battle or only now obtainable on that character due to it being on only another character previously or whatever, it doesn't seem to do anything at all.

Furthermore, GetCompanionInfo continues to blissfully unaware of new pets with the same restriction. Since dismissing seems to not care whether the pet is a duplicate or not, so you could possibly check for the pet's existence using GetCompanionInfo, and call DismissCompanion or the C_PetJournal function accordingly. (Probably DismissCompanion is doing its own check to make sure we "own" the pet, and it isn't from something else)