I disagree with this very much. There are a couple of schools who only told me I was on a waitlist after I inquired. If it weren’t for these emails, I would've accepted another offer. There's also a school that told me you are accepted and sent the offer a month later. If I hadn't inquired, I would have been worried about this school for an additional month.
One of my friends also was told by Northeastern that he was on a waitlist and that we would hear back, at most by April 16. Since the other offer he had (UKY) expires on April 15, he asked the school that admitted him to extend the deadline to April 16 so that he can wait for Northeastern's decision.