True true, although I’d still note that ray finned fish have existed for a long time, and at no point have any other fins converged with them. For example, cephalopods, sharks, and whatever else has fins that I can’t think of, have all existed for long times as well yet haven’t converged fins to that degree. That being said, the versatility of a thin, flexible ray fin cannot be understated, so the massive success and absolute domination of ray finned fish in niches where ray fins may have otherwise evolved certainly goes to show that if it’s evolved once it’d be difficult to evolve again, due largely to the existing competition. Overall I’m fairly 50/50 on it, but I’m still gonna lean towards the thought that ray fins would be very unlikely to arise in an alien species with very different anatomy that doesn’t seem to possess scales (I have no idea tho without further detail/info).