I'll also add my observation that most of the college coaches have relationships with other coaches from other divisions. In other words, say a kid goes to a JUCO and wants to play at a DI school. That JUCO coach will likely have any number of DI coaches that they work with and make recommendations to. The DI coaches rely on the trust they have for that JUCO coach and their assessment of a player. And that JUCO coach is NOT going to recommend a kid to a school when he doesn't think that kid will be a contributor. It would ruin his reputation. JUCO coaches will also have contacts with DII, DIII and NAIA coaches and will try to get their kids referred to the appropriate level of program.
From the other direction, probably every DI coach knows he will have kids that are not going to make it in their program. They will often have relationships with coaches from other levels to refer the kid to.
I think these relationships are much more important than what a kid scored at a PG showcase.
Also keep in mind, if a kid wants to move up from an NCAA DII or DIII team to a DI team, the sit out rule applies. Going down from DI to DII or DIII, there is no sit out rule. Nor are there sit out restrictions between NCAA and NAIA or JUCO programs.