I don't know if any offers are official in a contractual

sense until the student-athlete receives the National Letter of Intent to be signed as the final step of the recruiting process. Certainly schools can send a letter confirming their early interest or offer as part of the recruitment effort. I know that lacrosse is moving its recruiting calendar toward not allowing commitments until the beginning of the junior year, which makes sense to me.

Some WBB programs seem to make early offers to many prospects. Louisville and South Carolina come to mind. I believe that many of these are honorary as a way of building interest among prospects.