You can't just turn up clockspeed and expect linear increase in performance. The chips are packed so dense with transistors that the chips have to do some magic to be able to operate at those clock speeds without frying. Desktop parts don't really care about energy efficiency and are thus designed to be able to operate like that since max performance is more important than efficiency. Microarchitectural design decision allow engineers to pick tradeoffs for where they want to place their chips in the market, but most major advantages between chips come from fabrication. And these days there aren't much gains left to be made there.

CPUs are designed with a certain clock speed in mind. The target frequency affects the design of literally every component. Turn up the frequency too high and signals won't arrive in time. Increasing the frequency to match performance with AMD and Intel might require an almost complete redesign.

Maybe it can run faster given better cooling and less aggressive power-saving. But I'd be surprised if it can be made to clock much higher, else Apple would have done it already. Mobile CPUs already have peak performance well above what they can sustain. An even faster turbo would be used more rarely but would still be useful.