Junior year "commitment" for an Ivy is the same as any other school. There are no special circumstances.
Coach likes what he sees, kid has a good 9th and 10th grade transcript., and coach gives an "offer." Most dont have testing done by fall 11th grade - but many have PSAT results which have a degree of correlation with a real SAT. (Back in the time when subject matter tests were required, my son was still missing those scores during the OV. When I asked during a pre-read what did the school do, I was told they "assumed" a score which would be consistent with the ACT. But that the "assumed" score needed to be delivered.)
Ivy admissions requirements haven't changed. All risk is on the player to deliver whatever is needed; so, a perfect 9th and 10th grade can be undermined by 11th grade grades (12th grade grades are different).
The only thing which has changed since we went through it is "offers" are being made a year earlier. There is more academic fall out, however, because required elements of the academic resume haven't been completed.
(One step a family can do is to get that testing done as early as possible. Except for the truly "on the academic bubble" player, the coach KNOWS who he can get in. So e.g., the coach knows that a kid with a 3.9 unweighted through 5 semesters of HS, with the most rigorous courses, and a 33 ACT will get in (even if kid drops during 6th semester, the GPA is still above any minimum).
BTW, there are still open spots for that rising senior.