I imagine releasing server-side changes to Google's core search functionality is quite a bit harder than releasing an extension. If nothing else, there are tons

I imagine releasing server-side changes to Google's core search functionality is quite a bit harder than releasing an extension. If nothing else, there are tons of tests that need to pass and there's probably constraints on speed regressions and such. This is a much quicker way to get the same data so that they can determine whether the data is actually useful as a ranking signal.