What? It clearly shows that 3 people speak at discord right at that moment while they also play at 1 table.
This could have been any 3 people and if the chatting is happening outside the platform, I'd say there's nothing they can do.
Of course its no solid proof. But even having the possibility must be against house rules.
Even with the possibility of it being against the house rules, there is absolutely no way it can be monitored or enforced.
You see people at live events chatting via messenger while sitting on the same table? I bet thats illegal as well.
Cheating ? Absolutely. Illegal ? I'm not sure according to which jurisdiction.