Of course but what if he decides he wants to leave earlier? Then it's a case that nobody can pay his fee and he's stuck there.not really, if he signs a 5 year contract now he’d be 26/27 with a year left on his contract there. Now the release clause could be a billion but if he refuses to sign a new contract Madrid would either have to sell him then or lose him for free the next summer.
I don't think Haaland is actually desperate to bounce from club to club. I think he'll happily stay put under the right circumstances. However he probably (or certainly) wants the freedom to move should he ever decide that's his way forward.