I think the argument is (I'm no physicist) that quantum states and thus its computing happen in all universes and that's why it is so fast. But if we think of parallel universes where each possible decision creates another one then quantum processing would inherently get faster and faster with time? Or would it get slower and slower with more and more universes using quantum processors and thus hogging quantum states?
Either way, sounds like marketing bullshit, like the big "AI" hype behind LLMs.