Something claiming to be X doesn't mean it's X at all least good at being X. This option on tube TVs that I had never worked for commercials, works so well that I don't notice it on a "smart" TV.

If you don't want auto-brigntness you don't have to enable it. I have a hunch that a TV sets it better (just for the reason that you are unlikely to adjust every time you turn lights on and off) but tastes do differ indeed.