Human eyes have different perceptions of color, invisible light and visible light, and the changes of light and screen brightness will affect human eyes' feelings.
To give a simple example (taking the screen of a mobile phone as an example), suppose you will feel tired after 4 hours of normal use, but you may feel tired after 3 hours if you play with your mobile phone. However, if you turn on the "eye protection mode", because the color of the screen becomes softer and the color becomes what the eyes like, you may not feel tired after playing with your mobile phone for 5 hours.
But in fact, the eye protection mode only changes the color of the screen, so reducing the stimulation to the eyes is not really "eye protection".