I think Umtiti was persisting in delaying surgery to be able to play the world cup. Something that I don't see an issue with as the window of winning the world cup is small.
Looking at Transfermarkt he missed the last few games of 17/18 season with the knee injury that plagued him in the subsequent season.
The big issue was Umtiti didn't take the surgery after the world cup instead tried to play through it, aggravating it and leading to the mammoth absence of games these past few seasons.
Would it be wrong for the club to insist on surgery before renewing (because I believe they recommended it) the player to take time off before the issue gets worse? I am not so sure, we are a performance business afterall and health is requisite of this.
Of course it is easier for me to say in hindsight, perhaps Umtiti didn't have confidence in our medical staffs recommendations and given their failures, and wanted to take an alternative route through his recommendations. You couldn't blame him on that account entirely.
So there are definitely two sides, but from the my persective you just can't put such a big investment into a player that has a big issue which looks like it will develop worse if untreated. Because this is what happens. But we have made this kind of injury oversite almost customery back from signing Milito, Vermaelen to the judgement on Umtiti.
From a clubs stance, if a player does not want to take the route that your research shows is the best for the teams future, then you got to sell and re-invest.