While I agree with Chas points about spinning vs grinding general, we have to look at the amount of change we are asking about.
170 > 165mm is 3% change. So, even if there was an absolute hard and fast rule, it would still just mean you’d have to have a 3% change in cadence...
On an anecdotal note, I switched from 175 to 170mm cranks on my mtb and do not notice a difference. I am 6’5”, so 170 is very short in a relative sense.
I have never come across research indicating a big difference in power with crank length changes in the normal realm.