I think that's what Pogba wants. If he were on a free transfer, he could demand a much higher hand money in contract negotiations with his new club. It was similar with David Alaba, for example. He had rejected contract offers from Bayern again and again for a long time and gained time until Bayern could no longer sell him with a transfer fee. In the end, he moved to Real Madrid last season without a transfer fee and got a big hand money from his new employer.
Yeah, this is happening more and more often - especially after Covid reduced the transfer budgets of most clubs. Players simply wait for their contract to expire and then demand a bonus fee for choosing a new club.
The new clubs gladly pay it because it costs them less than it would cost for a transfer to happen if a player was still under contract and of course that the players like it more when they get the money instead of their clubs.
Regarding Pogba - I still feel he will extend with United. They are the ones currently ready to overpay once again.