I was referring to the extent of brightness variation in the flicker -- while many focus on a higher frequency (Hz) to reduce eyestrain, the key factor is how the screen behaves during the off cycle

Some PWM implementations ramp the brightness up and down slightly (easier on eyes), while other manufacturers flip the switch on and off harshly (like strobing)

The shorter time the screen is dark between being lit up results in a a shorter pulse duration, and the pulse duration and depth are more important than the Hz