The original is a gross over generalization. it depends what gear, what bike, and what speed.

You can "quick shift" if you know when the speed and the gear mesh. it has nothing to do with a specific RPM.

You can "quick shift" at 2k if you are going into 5th at 40mph.

It's just knowing your bike. telling someone that their is a "sweet RPM for it" is just wrong.

Unless of course you rebuild motorcycle transmissions, then... nice work.