Well, I suppose you might be right.
Would QF sue members who try to pass off mere friends as first cousins "fraudulently"? Maybe, but that's perhaps taking a sledgehammer to hit a nail, a waste of attorneys and what would be the restitution? As long as QF could claw back anything that was "fraudulently" gained (cancel points, bookings or accounts), I think they're happy to settle for that. If the member thinks they want their day in court to claw it back, then QF could call in the lawyers, but their objective (apart from claiming court costs) would still be staving off any loss rather than insisting punitive damages and/or sending the member to prison.
As for this person, there's verifiable monetary losses that can't just be "taken back". There's a difference between claiming falsely that someone is your cousin when they are not in order to transfer points to them or even redeem for them, versus misrepresenting yourself in a commercial contract in bad faith for tangible gain. I'm not sure if this might rise to a criminal offence in another jurisdiction due to the amount of money involved (and even if it did, how easy would it be to prosecute), but clearly in Singapore it's enough.