Is This A Thing That People Do?

This is a sign in the elevator in my building:

Sign in the elevator in my building

Run the dryer for 20 minutes after the laundry has finished drying to evaporate the water in the vent? Seriously? I’ve never heard of this before and it seems awfully environmentally unfriendly to do that. But then, I’m not much of a person for chores, so perhaps this is a thing that all people know you are supposed to do and you are all going to be “OMG, Beth, you haven’t been running the dryer for 20 extra minutes after every load of laundry? What is wrong with you??”

So tell me, Internets, am I crazy or are they?