I don't think the umpires got it wrong. Ginnivan's action is really hard to officiate, because the Freo players really did tackle him high so in real time they can be forgiven for paying those free kicks.
The AFL needs to see what Ginnivan is doing to instigate those free kicks as a pattern and tell Ginnovan to knock it off, and warn umpires not to pay it in those instances. It's the only way to stop players like him from doing it, and the umps rewarding it.
Had the MRO watched the whole game they would have some context for this incident, but I don't think they did. Freo should send the highlights of Ginnivan exposing that arm in the previous instances. It probably won't get Switta off - in all the circumstances he probably should have still released the arm earlier once they were on the ground - but the AFL needs to save Ginnivan from himself and spare other players being reported for sticking a legal tackle.