Yeah, this is kinda the only way I suspected they could be marking cards. Most card-marking schemes don't allow you see what's coming unless you're nail-nicking or otherwise marking the sides.
What's incredibly foolish about this is that they could have made a lot more money and stayed in the game a lot longer if they'd been slightly more cautious about how they ran the scam.
Don't play quite so many raggedy openers, don't do obvious collusion stuff like whipsawing, and in general don't be such a sore thumb. The stuff Anthony has described them pulling is the kind of thing cheats should reserve for when they're ready to burn a game and move on. Their day-to-day scam should be much subtler if they're trying to run it long-term. Without all these glaring red flags, it might have taken a lot longer for anyone to start digging and eventually notice the marks.
Of course, on the other hand, we should be glad that most cheats are too arrogant and reckless for their own good.