It just happened to me, where I added a "-word" term to narrow it down and the number of results increased somehow. That means that they're doing something behind the scenes that's not as simple as "remove all results that contain "word".
A tangent. You have what I imagine is a hard job and, despite the many threads here about recent apparent quality decreases, the product brings enormous value to its users.
Thanks for taking the time to discuss in this thread, it is very helpful to see your insights.