I think they have to if they are serious about keeping him. He will get at least 2-3 max offers from other teams like Knicks, Clippers, Nets and he isn’t taking a discount this time.
I’m not sure if this will turn out to be a good deal though. He turns 31 this year, he was always going to get worse during the length of this contract and with this sort of injury it’s almost certain he will never return to his top form from this year anyway. He’s still likely going to be a damn good player but you would be talking more All-Star level at best than HOF level. Hope I’m wrong about it but few players returned from Achilles and were good, let alone great.
Also I think it’ll be bad publicity by Warriors to not offer him that deal now. Regardless if they pressured him to return or not, they are at least partly to blame for this injury I feel, or at least this is going to be the perception around the league.
It’s also the best situation for him to go to, as pointed out by Nate Duncan. He knows they will be in the playoffs and a contender and if he goes there and plays from March onwards he can still contribute to a championship. If he goes anywhere else it’s far from given he will even be in the playoffs. Knicks without him are definitely not even close to a playoffs team.