I’m seeing this way too often. It is a good idea to never ignore a warning, an developers without discipline may need it. But for god’s sake, there is a reason why there are warnings and errors ,and they are treated differently. I don’t think compiler writers and/or C standards will deprecate warnings and make them errors anytime soon, and for good reason. So IMHO is better to treat errors as errors and warnings as warnings. I have seen plenty of times this flag is mandatory, and to avoid the warning (error) the code is decorated with compiler pacifiers, which makes no sense!
So for some setups I understand the value, but doing it all the time shows some kind of lazyness.