It only switched your search engine if you'd never changed from the original default (Google). If you had ever switched the search box to use a different engine, FF continued to respect that.
But why would I change it if I wanted Google, which incidentally is, I'm sure, what most people want? Leaving the default can be as much a choice as changing it.
(I'm on Mozilla's side in this discussion, but that particular move was terrible, even if not too consequential, in my opinion.)
