La Liga have basically responded and said Messi took the meaning of the end of season out of context.
But the end of the season was the end of the August. Technically Messi is right. It states in the contract the end of the 19/20 season.
Two different things. One is that the 700M evaporate in case he unilaterally terminates his contract at the end of the season. The other is HOW the unilateral termination is possible. We don't know whether there's a clause defining that. If not, Messi is good to go. If yes, it depends on what's said in there. In that sense: Yes, the context is lacking.