I wouldn't say anybody measuring input latency at all is common, but if I were doing it I'd use https://isitsnappy.com/ https://isitsnappy.com/ or some other hi

I wouldn't say anybody measuring input latency at all is common, but if I were doing it I'd use https://isitsnappy.com/ https://isitsnappy.com/ or some other high speed camera frame counting and check the time between when your finger starts moving and the screen changes.