FWIW,
If it asks for the HS coach that is what they want. If they are serious they can find out who he is and contact him anyway. You can also include his summer coaches contact info.
When we send out questionnaires with specific questions like HS coaches contact info and we see someone else filled in... It appears that there is a problem with the HS coach and someone is trying to get around it. That doesn't make much difference to us, being we hardly ever contact the HS coach. However, if I were serious about recruiting a kid to a college, this red flag would cause my first call to be to the high school coach. I would want to know why he wasn't listed.
BTW, most college recruiters are used to high school coaches. The ones they trust carry a lot of weight... the others they don't trust. That doesn't mean they don't listen to their opinions.