That said, I have a small nit. I would have liked to see how performance changed relative to the same time last year, to control for seasonal effects. Image 1 is showing changes on the scale of 1/100 of a second. I'm not an expert in the field, but when you'r looking at signal of that magnitude controlling for noise is more relevant.
EDIT: I should add, I am a satisfied user of FF.
Edit- also see https://wiki.mozilla.org/Areweyet
It looks to my naive eyes like the trajectories here are consistent and that the “signal” looks bigger than the variance. The measurements seen consistent with a bunch of smart engineers working to optimize for them during the time period they were measured.
At the same time you’re right: that big August improvement might well have something to do with Northern-hemisphere people switching to lighter vacation reading rather than just the Firefox 116 release happening to drop August 1. I’d share your interest in the longer timescale.