I would say that low humidity is not a bad thing because with low humidity you also decrease the chances of mold and bacteria getting at your plant. My humidity is around 30%-40% with lights on and my soil is moist, my cousin use to grow his plants outside in nor-cal, and his plants flourished in his backyard in summer time, when the humidity is relatively low.

IDK who started a higher humidity the better but as far as I am concerned it is not exactly true.

I vote low humidity is best, regardless of what others might say.