Congratulations to your son. It's exciting to receive that kind of letter. If you received notice from one advisor, you will probably hear from others if your son is on the "shortlist". Approach this process carefully. Check out who you are dealing with by asking for references. I actually called the parents of the players that advisors handled. I felt that was my best source of information regarding how the advisors handled their sons and I asked them if they would use the same advisor again.
Bottom line: I would ask the advisor who his sources are and to define to you what a "short
list" is. I would ask for references and check them out. Also, I would ask this advisor if he has ever seen your son play. If he hasn't, he may just be fishing, casting out the net to tie up as many players as he can.
As an aside, after we were notified my son was drafted, it wasn't five minutes later before our home phone rang with an "advisor" 2000 miles away wondering if my son had representation. Advisors are much more than contract negotiators. The good ones are part of the process at least 6 months to a year in advance. Good luck to your son. Take care.