i was about the finish the best stall ever but when i tried to use it on ladd, it said that Shedinja is actually banned in AAA for some reason...is it on purpose or just some error?
Yeah. It gets access to Sturdy. That's why Shedinja is banned, and why Shedinja stall in AAA is never going to exist (unless the higher-ups say otherwise). Also, complex bans are usually not implemented, so this is intentional, and very unlikely to be reversed.