Seems more like an oversight or a misunderstanding of the legislation rather than anything malicious or 'cheating' to me.
Probably similar to what happened to Bradford when they were found to have breached the cap, and that was actually in a year where Bradford won the GF.
You have to laugh at the timing of it though. The RFL statement says that the decision was reached last Thursday. So they've waited until now, the eve of the new season kicking off, to announce it