Without a doubt what you're describing about HS coaches are contacting assistants is exactly as you say. That 100% is the primary way, I suspect, college coaches find out about guys they don't already know about.
Let me be clear that I don't believe many legit college coaches troll the recruiting databases out there. I tried to indicate that by saying I thought it was simply a potential use case and we GT folks all know that potential just means it could happen, not that it does. And if a coach was looking in the recruiting databases the way I would see it happening is that they're looking to fill a spot and someone they know tells them there's a kid out there and there's some basic info on him in the Rivals site and they go look at the page and see where he goes to school and where he's from and maybe they even view the highlight reel (though if you've ever watched one of those you'll know it contains only positive plays and they're hard to see even on a large screen) and then find a way to contact the coach at the kid's school to take the next step. I don't think they look at the rankings even a little bit.
So overall I think we look at it the same way.
Coaches network like they always have..... and from both directions, it's all about who can you trust.
No college coach wants to be pimped nor have his time wasted about a HS player who can't compete and contribute at that level. HS coaches don't want to be lied to and their kids misled.
Today's off-the-field GA's & staff do a lot of the groundwork, watching video, and doing evaluations before the area/position coaches get asked "Whattyathink?" In situations where the area/position coach has a prior relationship with a HS coach, it's obviously different. And the area/position coach has to be able to give the HFC an honest, accurate opinion and evaluation of why a particular player should be offered over someone else.
College coaches want to use the Mk1Mod0 eyeball to evaluate the talent and today's camps provide increased opportunities. It's not all about just watching a Friday night HS game any more....
But recruiting services run by wannabes/jock sniffers? Not so much.