Cryptocurrency exchanges would have to be registered with the authorities in Russia before they can operate in that jurisdiction, so only authorized services are allowed to operate. However, this aspect is consistent with what you can find in other parts of the world. Russian banks are also going to reject tx's if they suspect it's from unauthorized entity:
given that operating in Russia is limited by a multitude of sanctions there are serious doubts that any global crypto exchange will register there. I think this aspect is consistent with some countries like Iran where only local crypto exchanges operate. in my opinion they'll have to create domestic exchanges and I suspect there won't be many people willing to work on them, even among local users.
To be fair though, your funds can be seized in any crypto exchange operating in any jurisdiction, for any reason!
I absolutely agree about the possibility of confiscations on centralized exchanges but it's unlikely they'll do it for far-fetched reasons. for example, in Russia they could seize your assets for saying something about stopping the war or demanding Putin's resignation.
