Blurb about effect of grinder RPM (especially for hand grinders in entry level)

[simonyangme]

Grinder RPM has an effect: https://www.baristahustle.com/blog/coffee-grinder-rpm/

Starting out in espresso is frustrating enough, and this seems to be a thing that isn't mentioned enough but adds enough inconsistency to make learning more frustrating. Slower and consistent speed will generally give better grind quality and make things more repeatable.