This seems far more simple if the right to terminate the contract was tied into the end of the season rather than a specific date. FIFA had already confirmed the position in relation to the extended season and the clause is therefore clearly in place to allow Messi time to reflect and decide once the relevant season has been completed. It would therefore be reasonable to accept that, due to Covid, that time would be to the revised season end and not still back in May/June.
La Liga's response is to be expected. They've seen Neymar, Ronaldo and now Messi look to leave so commercially they're in a weak position compared to a few years ago. What other headline players are there that would make people want to tune in? A few rising stars but you'd watch English, German, Italian and probably French football before turning to La Liga if Messi leaves.