I think that's just what is going to happen. I bet the anticipated time table is shorter than we think, and that played heavily into the decision to go ahead and get it done now.
Like it is indeed only a partial tear as stated up-thread, they are confident in the procedure/quality of rehab, ability for his body to repair itself given his young age, and so on.
It's a cost vs. benefit calculation: get a top 10 talent in a year when you don't have a top 10 pick via paying the price of him missing a month (let's say) of his first season, with plenty more good football years to follow.
Who's to say if this is the right or wrong thing to do? I like the "go for it" approach to be honest.