Known both in KSP and space industry as "asparagus staging", it's a pretty old idea. It's tough to implement in real life, though, because pumping fuel around adds a non-trivial amount of complexity to the rocket. FH might be the first ever production rocket to use it, actually.

EDIT nevermind, I didn't realize SpaceX scrapped the idea too.

I thought they scrapped the crossfeed fuel idea because it was too complicated?

They did.