Within those specifications, the objection about the ad-block become irrelevant. If the browser justs works better, then users don't care and can simply enjoy more battery time.
The case for more normalized tests is to find out which browser is factually better designed/written.
Why is a different question and it's not that relevant, I often don't care why something I USE works better I just care that it does.
If it something I BUILD then I would care much more but again this is a whole different issue.