My bet is that they don't. My bet is that there is so much old code, weird data edge cases and opaque machine-learning models driving the search results, Google's engineers have lost the ability to predict what the search results would be or should be in the majority of cases.

SEO experts might not have insider knowledge, but they observe in detail how the algorithm behaves, in a wide variety of circumstances, over extended periods of time. And if they say that deleting old content improves search ranking, I'm inclined to believe them over Google.

Maybe the people at Google can tell us what they want their system to do. But does it do what they want it to do anymore? My sense is that they've lost control.

I invite someone from Google to put me in my place and tell me how wrong I am about this.