Unlikely, the contributors don't seem to have meaningful Ruby backgrounds. Isn't it a simpler supposition that the naming intent was merely (R)ust Actors?

well, it's "r" + "actor" - just a coincidence that both "ruby" and "rust" started with an R!

I have to wonder if Ractor was inspired from The Diamond Age.

Yeah bad choice of naming here. Oddly this project shows up first on DDG for “ractor” despite prevalent Ruby ractor documentation.