Misdiagnosed is probably the wrong word. My gut feeling is they thought X was wrong, and they tried to fix X, but were unsuccessful or 80% successful...
I agree. Bakhtiari seems like a proud, honorable guy, and I suspect felt an obligation to get back as soon as he could, since just before the injury...
To me it clearly sounds like they misdiagnosed the injury the first time. It sounds like it was more than the ACL and they limited the fix to the ACL...