First of all, I don't know who ever said that "tools" don't matter to a scout, recruiter or evaluator, but that is not accurate to start with. Of course tools matter. Maybe someone said in-game performance may not matter, depending on what tools the player shows, but tools do matter. And I'm not exactly sure what "base" you are talking about. Do you mean velocity, 60 time, pop time, etc...? An athletic soccer player will probably not be able to come in and score a 6. There needs to be SOME baseball skills there to garner even that number.
Of course the PG evaluation will give you an idea where your son stacks up. If he gets a 10, he's a super talented player is is looking at a minimum of a D1 opportunity. If he's a 6, he's probably an average prospect. Some baseball tools, but he has a LOT to work on. My son was an 8 his first showcase and an 8.5 his second showcase a little over a year later. He wound up at a top D2 program. That's probably where he belonged. Just because he was not a 9 or 10 didn't mean he wasn't a college prospect.
CaCO3Girl, this stuff is not set in stone. I know you have a scientific background and like concrete information. Evaluating baseball talent is not like that. There is no if you are a 10, you'll go D1, if you are an 8, you'll go D2, etc... Beauty is often in the eye of the beholder. There may be a 10 that goes D3. There may be a 7 who goes D1.
Suffice it to say, the higher your number, the better your tools showed at that showcase. The lower your number, the more your tools did not show. And yes, a big part of the evaluation is based on things like speed and velocity. However, there has to be some baseball acumen there as well.