Nebby still used it multiple times, so the point stands. 4 times certainly isn't a negligible amount of time no matter how you look at it. Nebby still was a recurring Pokemon which was along with the cast for some time no matter how much you want to overlook it.
I already said it could be very much the case where Torracat evolves soon afterwards it learns Fire Punch, so in that case, the move error won't last for long, so I don't know why you keep bringing up this point that Torracat would be around for a lot more episodes than Nebby.
Noibat/Noivern's move was certainly Supersonic, it was even mentioned/commanded multiple times as Supersonic. In Nebby's case, it was nothing much different, and I can bring up multiple site/sources which state the move as Supersonic:
https://m.bulbapedia.bulbagarden.net/wiki/Nebby
http://pokemon.wikia.com/wiki/Nebby_(anime)
And even if you still want to argue that the move was Screech, then that doesn't also help your case, because Cosmog can't legally learn Screech.
Nebby was a recurring Pokemon on the main cast so it isn't too much different either.
It could also be a case where Torracat evolves soon afterwards into Incineroar after learning Fire Punch, so in that case the move error won't remain for a long amount of time.