I understand that they may kick you out for being too good (he must be "cheating"). And the argument about using a device to aid you might be a more concise definition of cheating of some sort. But I've never noticed any posted rules that one would reasonably be expected to know about. And the use of the term "fraud" is important because then it becomes a legal issue with big consequences beyond getting kicked out or banned from a particular casino. OTOH a casino doesn't need to post the law for people to read. Does the law defer to the casino rules? That wouldn't be appropriate IMHO.
There are "house rules" and there are laws. I'm kind of wondering where those lines are and what specifically these guys did that constitutes a felony. What specific aspect of their scam was illegal. I'm not disputing that it was dishonest and in effect a scam of sorts.