I don't get your objection here. Not only does high-performance mode eliminate OS-level confounders that would otherwise render consumption deltas highly questionable, it does so in a way that produces worst-case results.
All that other stuff impacts battery life in a huge way. Those variables matter. You can't just remove them, call it a "worst case scenario", and walk away. That is not valid.
When a reputable site like Anandtech reviews a laptop, they don't force it to maximum performance mode, because nobody that cares about battery life would ever do that. It's testing a scenario that _doesn't matter_.
In fact, not only is it not the default, but maximum performance mode doesn't even _show_ by default-- you need to expand a "show additional plans" dropdown in the power control panel to see it. Opera went to the trouble to do that, and it was not by accident.
I think you're looking for a followup study that complements these results, but that study would be not as valuable as with these to inform their interpretation.
What exactly are you complaining about?