If I had a large query set to run on each vendor I'd be more likely to hit compatibility issues which could mean fewer benchmarks going out. As it is I spend a lot of time getting hardware and software vendors together for these benchmarks.
If caches were being hit I'd expect a lot more DBs hitting single millisecond times in my benchmarks but as far as I can see, there is a clear delta between the various setups I've tested:
I hear you about compatibility. I think this benchmark would be greatly improved by rewriting the query to include a subquery and a fact-to-fact join using the same table. For example, you could do a subquery where you find the longest and shortest ride for each driver each day, and then join that back to the full table and calculate something. That would do a much better job of exercising the key features of the query planner, while still being simple and compatible.
Even without those though, this is a good read, thanks for it!