That's more than a hint. If it's removed, especially lava on a Metroid stage, it must have interacted with the stage somehow. Not that that really proves Ridley's not a boss. It just proves Ridley would be a boss you have to deal with on top of a lava hazard.
Also I seriously doubt Ridley somehow follows a different aging process than Roidley. If anything, I would imagine Ridley might have spent more time growing than Roidley did. But yeh, that doesn't really matter much since the real interesting part of Ridley's evolution is how he goes from being an aduld space dragon to "Meta Ridley", "Meta Ridley II", "Omega Ridley", and "Ridley Reborn". Meanwhile, Roidley, who people don't really like, becomes Ridley X which is the worst Ridley there has ever been. His resume isn't great.
And I don't know if Sakurai "knows" we don't like Other M Ridley or not. But I do know he is basing Metroid content off Other M. I mean he COULD be making a playable Ridley that looks intentionally out of place, OR it could be the reason he is redesigning Other M Ridley to be a sort of "hybrid design".