It's more complicated than you're making it seem. Anyone can raise any AML governance concerns; what's important is if the concerns are reasonable and resolvable without excessive or unreasonable costs and resourcing, and would yield significant real-world benefits.
ISX's claim that no AML breaches have been reported through its networks supports the claim its framework is/was fit for purpose to some extent.
Also, the relationship was going to cease anyway, since Visa was making changes to its SDWO rules and I think was requiring ISX to use Visa-issued account numbers for flykk, which would break the current IBAN model and make it incompatible with other schemes.
ISX Price at posting:
$1.07 Sentiment: Buy Disclosure: Held