This is their attempt to save their face and also to increase the initial fee. It's normal. They are the seller. They have to do it because United have as much as power as them. Because right now, United are the only one that could pay and want Sancho. City are the other that could pay but the chance of him returning is zero. Dortmund has no other choice than to bring up all sort of dramas into play because currently there's no other realistic demand for Sancho.
I don't think it's as easy keeping him for one more season for Dortmund (so that they could sell him for higher profit a.k.a 'post COVID there will be a lot of takers') because:
- Nobody knows how long it'll take for the global economy (especially EU) to return to it's previous state. Even if the vaccine is found one day, the economy recovery will still take time. It's useless to predict such a thing and the Dortmund board surely know about this. There's a lot of uncertainty
- Sancho will be on his last contract in 2022, which means his value will normally be lower, without taking account of the number of demands in the future
- Keeping an unhappy player (considering Sancho really wants the move) could only lead to disaster, delaying his replacement process when they know he'd leave at some point and this could also affect his performance. Dortmund doesn't seem to be that kind of club, they want value first and foremost, if they could secure the result of their investment now, during a very volatile economic situation, why not do it?
So basically there are two options for them. Be a greedy bastard and rely on uncertainty or secure their investment now (that have grown by a lot) and plan for the next one, without having to worry about how the economy's going to be. It's a no brainer, they'll sell but not without a fight. They negotiate and there's nothing wrong about that.
But at some point there will be a middle ground between the two clubs. It's still SanchON.