I think you (your son) made the right decision. He's a 2020, correct? My son gets a ton of camp invites from coaches who have seen him or whose assistants have seen him a a camp or other event. My thoughts:
1. It they are REALLY interested, why not call or text? He's a 2020 so there is nothing stopping them from doing so.
2. If they saw him at the event (especially the HC) then they must not like him enough so either they want to see more or they want him at the camp for his $$$.
That being said, I think some may just be gauging his interest in their school/program. Especially D2/D3's. But again, why don't they just call or text? If they are truly interested then let that recruit know that!
I'm no certainly no expert on this as my kid is not yet committed. But he does have several D1 offers and although rankings aren't everything, he is nationally ranked and has received pro interest (MLB Draft Prospect Link invite).
So when I see the camp invite vs. direct contact I'm just a bit suspicious...