Guess it depends what he means by "stiff" though. So far I've been reading it if he tightens down the cranks it makes it hard to pedal, which would suggest a missing or too-small internal spacer.

He might just mean that the cranks don't swing around unless you actually tell them to, which you want if you're doing anything off the pedals (you don't want to land and find your cranks aren't where you left them...).

On one of my other bikes the cranks will happily backspin for like 30 seconds if you give them a good kick, which I thought was awesome until I gave them a kick around ready to take off from a set of lights and smacked a pedal into my shin. You don't want this.