You’re conflating issues here.
The only way players can be paid under NCAA rules is through NIL where they sell the right to use their name, image or likeness in exchange for payment. But Oscar can’t do so because of his visa status. Thus, that poster was suggesting that he might be able to get around it if a Kentucky business essentially disguised it as an NIL deal with his mother, and not Oscar. If investigators saw through that scheme (as they surely would) then, yes, it could still be regarded as a violation of federal immigration law.
As for simply giving his mother money, that would not violate federal law, but unfortunately, it would likely still violate NCAA rules. The same rules forbidding schools and boosters (.ie fans) from simply giving players and their families money still apply.