It’s not so much a matter of cheating but having access the third party deals.
Or it's actually cheating if those deals are supposed to be at arms length from the club. The only reason that incident got picked up was because it got mentioned by a player in an interview. It's likely they were organisng deals like that before and maybe even after.
It's in the NRL's best interests to maintain an image of an even comp, fans would be disengaged otherwise and sponsors would not want to be involved. Seward was doing questionable things at the Bulldogs under the guidance of his 'mentor', Broncos weren't investigated with the Andrew Gee incident, nothing came of the cowboys/cheap property deals and the sharks were miraculously under the cap the year they won the comp. I don't think you can say with certainty that any team is not cheating. Even the shit teams, we won the spoon while cheating lol.