Yeah so you had two things (not) going for you:
a) PIDIV was invalid for wild encounters (so PKHeX determined it was an egg)
b) Future Sight TR was not checked (hence PKHeX determined it was a gen 3 egg move)
Also I just noticed: why does your Slowbro have a Gen 3 egg move (future sight)?
If you want to teach it a TR, you must make sure the TR table is checked. That's probably another reason why it won't flag legal.