I have a similar issue with my card (TUF-RTX3060TI-O8G-V2-GAMING) using 516.59 nvidia drivers
and GPU Tweak 3 app.
While I can set up custom fan curves ok, these custom fan curves do not behave exactly the same as the
default (Auto) profile fan curve. With the custom fan curves fan speeds differ quite a bit (especially at lower
speeds), while with the default fan curve they are pretty much uniform.
I must admit that the default/auto fan curve is very very quiet, I still prefer to use a custom fan curve
where the fans do not start at a whooping 53%.