so if you have a faster cadence/rpm's using the same gearing, then you faster ... a shorter crank gives you a faster cadence...
That's a big if.
If you can turn a faster cadence using the same gearing then certainly you go faster.....but you need to generate more power to do it and maybe you can and maybe you can't. A shorted crank does not
give you a faster cadence, particularly against increased resistance. It may allow some riders to spin faster but they may also need a lower gear to do it.