I've installed paint protection film for nearly ten years on over 3000 cars (6000 mirrors). In all that time I have run across 2 instances where the film on the mirrors caused a whistle. The first one was about five years ago on a first generation Porsche Cayenne and the whistle was caused by a small edge that was tucked between the gaps in the mirror instead of trimmed off, the second was on a 911 just a few weeks ago that I did not do the install on.
Replacing the film solved both problems. I guess its like blowing on a blade of grass, if an edge is not totally sealed and is in just the right place, its a possiblilty but definately not the norm.