I have never had any lag on my XL. I was one of the very first owners...Have never reset it. If an app was laggy I would blame it on the App.
If you wanted to create delay and pass it off as an issue, you could do that easy enough...First thing I would check is animation scales, and animator duration...I keep mine all off.
There may be a phone as fast as the Pixel...but there are none faster. That includes the new iphones and anything running a 845. Hardware issues are pretty rare and easily identified. In the Pixel case covered by warranty for 2 years. Most slow downs are software...(Read badly coded apps, The engadget app was one of these, now fixed)
I am guessing there are a million Pixels like mine that are lightening.
I take any reviewers opinion on anything with a grain of salt...They depend on clicks...