The tool was never fully tested for gen 7 as I couldn’t get RAM dumps for the generation. It could also be likely that the Pokémon could be in a slightly different format.
Probably, but it does also seem specific to Mismagius. My Honchkrow that was a gen 3 Murkrow went through just fine. So maybe they just forgot to say it was Okay for Mismagius when they saw they'd already okayed Misdreavus . Idk, its weird though