The article linked is perfect and explains this very well. The transmission is connected to the rear wheel and moves at a static speed, once you disconnect the clutch engine RPM drop. This causes a difference between the engine speed and transmission speed, the longer you take to shift the lower the RPM's will drop and the worse it will feel (if not rev matching).
Rev matching is to blip the throttle to more closely match the engine speed to the transmission speed to prevent abrupt engagement which causes the wheel to spin. Also even if you're not rev matching if you're not using the clutch as an on/off switch you probably shouldn't be locking the rear, remember to be smooth on clutch out and not to dump it . Slipping the clutch out more slowly (even if a very small difference) allows more TIME for the engine to speed up and the change won't be so abrupt.
If the R3 had a slipper-clutch, this would never happen.
I don't downshift to a lower gear unless the RPM's are in the lower range.
I also let the clutch out slowly, to prevent the jerky reaction.
I don't like "blipping" the throttle, or trying to rev-match, so I just make my downshifts at lower rpm's.
It's all about engine-braking, and gearing. It's simple physics. Rotational mass. Enertia. That kinda thing.
Dat moto lyf yo. :laugh: