I also have an S21 just going through this process, so I know a bit, but not as much as those that have been there and already done that.
First, the single best thing you can do is go to the Athletic Recruits forum and read every thread about pre-reads. It is a tremendous resource,.
As for your situation, it depends on the school. Not every school does a pre-read fyi. In my experience, though, coaches don’t want to waste time on a kid who can’t get admitted to their school. So they ask for grades/scores to see if the kid has a chance, or is a nonstarter. Usually they are familiar with what the Admissions Offices will require, though, obviously, they are not the Admissions Office.
So, just asking for grades is not a preread. My son has had a handful of pre-reads, and in those cases, the coach explicitly said “I will submit your materials to Admissions for a pre-read”. Although all of them had my son’s grades already, each sent an email asking for several documents: an official transcript of his grades through junior year, a school profile, any SAT/ACT scores, a graded paper (probably b/c this year not everyone has test scores), and in one case, a resume of my son’s extracurricular activities.
Your son should be the one communicating with the coaches and asking questions at this point. It is absolutely fine for him to ask where he stands. Clearly the coaches are interested because they are in conversation with him. My son would ask “Can you tell me where you are in your recruiting process?” as a way to see where he fell in the mix. He could also ask something like “Can you tell me about the pre-read process?” I know my son would not want to ask a more direct question, like, “can you tell me where I am in your recruiting list?” but I suspect that question would be fine.
Another helpful thing, if applicable, is to have your son’s coach reach out to the college coaches. They can have a more frank talk and your son’s coach can advocate for him. (If it’s a sport where this would be applicable).
For schools that do pre-reads, I believe it is a two step process. First, the player has to be offered a pre-read, and Admissions has to say that the player would be admitted if the coach wants them. (At this point the coach would let your son know that he passed the preread, or didn’t). Secondly, the coach then has to make an offer, and say explicitly “You have a spot on the team and I will support your application with admissions”. Not everyone that passes a pre-read gets an offer. At the point that an offer is made, that’s the time (I think) that a parent could get involved and make sure the player has understood the situation.