As Ogiewon says, the “builtin” functionality has a “default” The Fan is Spinning Up at high load.
The mentioned “settings file” is only used to change defaults. to i.e lower “tress-hold”
I assume you have used “Pi Imager” to install your HAOS-Image, Specific for PI5
There are quite a few Topics in regards to PI in here, Below is 2 relevant, thou “older”
How to access config.txt in Hassio? - #20 by DWiskow .
Edit ‘config.txt’ on Pi 5 HA OS 13.2 image? - #5 by evansnp .
Hope this will help you further, othervice i wouldn’t think alot of it, as Spiro said above, as long as it’s cooling, let it cool, it’s not like you save a tons of money by lowering the rpm, or tresholds of the Fan, and you might just risk that your “settings” is not Optimal