Author here: We did some research on enterprise websites, using the Fortune 1000 as our main cohort, and we found that only 13% of them were mobile-friendly and fast. This is in stark contrast to the number that are mobile-friendly (60%).
We're not exactly sure why performance lags so far behind mobile-friendliness, but we'd like to get some thoughts on this.
Thanks for the feedback. I think the safe answer is that your website is considered mobile-friendly if it passes Google's mobile-friendly test. Regarding popups, I guess most of them are built for desktop browser environment so they don't exactly adapt well for mobile. Popups suck regardless, but they do suck more on mobile.
We're not exactly sure why performance lags so far behind mobile-friendliness, but we'd like to get some thoughts on this.