Does the warning also apply in case I keep a low brightness always?

Background:

I usually sit indoors for any kind of work on my laptop. And my lighting conditions also usually remain stationary. The only change is day and night, where I would turn on the lights as the day ends.

I have witnessed that if I keep the setting "Automatically adjust brightness" as "ON", then the brightness keeps on changing when some kind of light falls on the laptop. Earlier I thought it must be because I am looking away from the screen or may be because the ambient light directly falls on its sensors or something.

However, recently I found that even with no change in the lights in the room, the brightness goes dimmer. Then I increase the brightness and then start typing or working, and again the brightness goes dimmer while I am typing. So, this is not due to inactivity.

Further, even with lights in the room on, I'd like the brightness to be reasonably low. That's how I find the screen to be comfortable to look at.

So, I turned the setting to "OFF".

Outcome:

System showed following warning message:

Question:

The warning says that "energy usage may be higher". I am assuming that that will only happen when the brightness is kept at a high position, even when a low brightness could have done the job. So, I am comfortable with that, as I will have better control over the brightness.

However, the next line says "Display and battery performance may be reduced". How so?

If I keep the brightness low most of the time and I control it manually, how does that affect my display or battery performance?

Please guide me whether this is just a warning applicable to people who keep their brightness at full all the time or am I missing something here?

[Edited by Moderator]