The OP seems to be referring to third parties posting on forums, so not sure we can speculate on the exact intent. Although it is known that these transactions often incur additional currency conversion charges beyond those advertised.
That isn't a valid justification though - they would be breaching merchant agreements by doing that, and it's still considered payment fraud. The whole purpose of the MCCs is so that transactions can be processed and managed correctly - which includes blocking transactions as required.
One of the reasons a lot of sites went to crypto-only is it introduces enough plausible deniability that everyone can blame everyone else, while still keeping the gravy train going. Admittedly things would be a bit more problematic if banks started blocking payments to crypto platforms.
Indeed, and as I mentioned there are two strands here - one is existing people using chargebacks as a last-ditched attempt to deal with rogue casinos; the other is potentially dishonest people using chargebacks as a way to freeroll the casinos (possibly in a similar way to SE fraud a few years back).
Which is why I mention intent being important - the first group have a legitimate complaint, the second group are potentially committing payment fraud given their behaviour depends on whether they win or not.
If banks are forced to act because of an increase in fraudulent chargebacks, either they'll continue to push more liability onto customers (as they have in recent years), or they will start introducing further checks and/or restrictions for foreign transactions.