moonpie your right that is very tiny. I don't think anyone believes the safe / not safe output on the opple as it'll show a device not safe when it is if it's dc like dimming/OLED for example. I just use it to get an idea for devices under 10kHz, mostly seeing waveform. Do those mini oscilloscopes have any noise that effects the measurement? They're cheap that's why I ask.
Other stuff as in different types of light measurements. I didn't say other things that cause eye strain. Speaking of that I would say color spectrum is definitely one other issue to some. We know certain phosphors on led backlit panels cause eye strain to some people which is easily detectable with a spectrometer. I know it affects me because the orange backlight on the daylight tablet caused me issues and it uses a specific phosphor (I forgot the name)