No.
Everton did terminate his contract.
Everton decided against suing him.
They then tried to claim £10m back in the P&S due to loss of transfer value, loss of paying wages and they said if they had have taken Player X to court, they could have got that back. The Commission - absolutely fairly so - said that there was no way to prove that. Meanwhile, Everton elected to terminate Player X's contract. It was the right decision, but they still made that decision, and since they didn't pursue any of those losses back from Player X, it was a rubbish case of mitigation.
It was probably the second-weakest of the lot, apart from the really, really desperate attempt at the transfer levy thing.