That point of "they're both from the source" has no meaning to this matter, so I don't know why you bothered to mention it. Which is why I'm saying your implication that you can obtain SR and SSR from the same gacha is irrelevant to being able to clear content in the game without relying on SSR himes.
And I'm not sure why you keep bringing up this R only hime ordeal. No one said anything about R only but you.