I wish there were some logic, but unfortunately, there isn't. I have already written about it several times, some providers are available to me in every crypto casino (BGaming, BetSoft, QuickSPin...), and some providers are available to me in some casinos and not in others (NoLimit, Hacksaw, Yggdrasil. ..), only Pragmatic was off limits for me in all casinos, until some new casinos came and now I can play Pragmatic in several places without a VPN.
I have asked several times what the trick is with those things, but I never got any "smart" answer, as it all depends on the license... So I am sure I can play ELK without VPN one day in some casino, but who knows when and where? Regarding VPN, several crypto casino reps have already written in their ANN threads that using VPN is allowed. I used it before just to play providers that were not available to me.
As long as someone isn’t using a VPN for multi-accounting or to bypass a self-exclusion or other type of ban it is generally acceptable at many casinos to use a VPN. It isn’t always the case so I wouldn’t take it as a guarantee and would be considerate of how much I’m willing to risk if they haven’t explicitly stated that it’s allowed.