NIL is still in its infancy and the approaches being taken have obviously developed/changed quite a bit even this far in. I'm genuinely interested to see where things ultimately shake out from a contractual perspective.
For instance, to avoid situations like you're describing, could the NIL payer for a given university (e.g., USC) include a "no shop" provision in any contract with a HS recruit - meaning, once the contract is signed, the recruit is prohibited from actively soliciting/entertaining offers from NIL collectives not associated with USC, taking visits to other universities, etc.? Let's assume for the sake of the hypo that the NIL contract in question is otherwise kosher legally. A "no shop" like that isn't tied to individual performance on the field, isn't a direct "incentive" for the recruit to go to the university, and doesn't appear (on its face) to run afoul of some of the other more obvious guidelines.
I know that might all seem ridiculous at first glance, but these recruits/athletes now have the freedom to be compensated like an executive (or business), and do that with the security of written contracts with sophisticated counterparties, so in that sense it's only logical that some of the same legal protections used in the regular corporate world ("no shops" are just one example) would be used for the NIL payer's investment.