Pretty solid for getting the “ok”. If the coach tells you the academic pre-read is positive, ask point-blank if you are being offered one of the team’s recruiting slots. If the answer is “yes”, then you should just about know for sure.
As for the letter. Well that depends on Admissions Office policy and discretion. The group of recruited athletes that receives likely letters is a sub-set of the group of recruited athletes who are admitted
And remember, a likely letter is nothing more than notification of admission (subject to standard contingencies) earlier than other applicants receive. That is all it is. Sure, in the stressful environment of college admissions and athletic recruiting, that provides great comfort. And it provides a tangible benefit if you are trying to decide whether to accept an athletic scholarship from an NLI school and need to make a decision by the NLI signing period–which may be scheduled to occur before the standard notification date for Columbia ED or RD admissions, as may be applicable.
The time to commit to the application process would be after you get confirmation that you had a positive academic pre-read and the coach is offering you a slot. In Ivy recruiting there is no “signing” (unless you wish to stage a replica of a signing). Your commitment to the application process is signified by your clicking–on the send button for the Common App and any Columbia supplements