Ok, curiousity got the best of me and I tried it. It makes sense for vacuum operator door locks, but I started thinking about how tightly sealed modern vehicles are and wondered if it might work on other locks. If you force air into the door one of the few places that will easily expand is the pop up lock, especially if the lock part is substantial like on my GTO.
So, despite protest from my dog for taking a Dremel to one of his prized tennis balls, I tried it out. With a dry tennis ball I don’t think it would work on any car. There simply isn’t a good seal between car and ball. But, once I wet the tennis ball I could tell the air was definitely going into the door. The locks on the Expedition and GTO didn’t budge though, so looks like I’m safe.