Mbappe may have reached a verbal agreement with Real Madrid and upon reaching a verbal agreement, asked Real Madrid for some time so that he could be released and then join Real Madrid, in which case Real Madrid may have accepted Mbappe's terms and given Mbappe one more season. Since Mbappé is very unlikely to stay at PSG, PSG should plan without Mbappé. And PSG may be planning how to prevent Mbappe from changing clubs as a free agent. In other cases where the club has full rights but in Mbappe's case it is completely different Mbappe's behavior seems like the club is responsible to him and not to the club. Maybe he will join Real Madrid as a free agent member as planned by Real Madrid. PSG may not be able to block Mbappe from changing clubs as a free agent.
This is business, if he wants to play somewhere else, he has every right to do that. But at the same time, the team has every right to try to sell him, or even if they want to, just bench him all season long, making him miss a whole season of his career which would be bad overall. Think about it, you are a player with a chance to have top 5 goal scoring ever career, and you miss a whole season, like injury but you are not injured neither, you get to play no games. They are free to do that if they want to, nobody could force them to play him.
Considering how rich the owner is, he could just ask for that out of spite and he wouldn't even feel the payment, it's nothing for him. That way Mbappe would still go to Real if he wants to, but he would be lacking about 14 months of matches when that happens.