I guess this is assuming that people don't just re-search with different terms if what they are looking for isn't right there on the first page.
Which I do all the time. I don't dispute that faster=better, but I have always been skeptical of Google's claim of just how much better.
That makes a lot more sense to me than her usual spin, which is that the extra lag discourages more searches.
There's are reasons Google might prefer reformulation and next-paging beyond just "ad impressions": it gives better feedback about user's intent for training relevance algorithms.
That is, they learn more from your second query formulation to get a better result than if you just find a good-enough result at #11.
Or, if you open multiple results in background tabs before deciding the best, by forcing you to express click-intent to get past #10, they get a stronger signal as to whether the top ten results were good enough.
(I always set my result count to 100, and often open 3+ results based on snippets, some from below #10, before viewing any of the target pages.)