I think it's actually disappointing for clubs to act like this i thought a release clause has been set on him before.
This is among the reasons that would affect players for giving their all to a club especially when there is an agreement for them to level before. While Haaland was much younger when he moved to City, Dortmund did well to stick to their word. For we can say City got Haaland for a cheap.
Because Sporting needs a lot of money to buy a new attacker to replace him, Sporting is looking to buy a younger players, and want to try make a "new Gyokeres". Sporting want to try make a club like Dortmund who always create great player which is sold at a high price. But for Gyokeres, I think Sporting must be realistic, 85 million Euro are not worth with his age. I heard Juventus want his service, La Vecchia Signora are trying to sell several main players to cover Gyokeres' price which I think will certainly affect their peformance on next session if several main player are not coverable by new player.