The nightlight applet should allow setting the temperature from gnome settings

Currently, only the applet can set the temperature. The gnome settings option will only configure the time that nightlight activates

The nighlight has a button to open the GNOME Settings Displays option where you change the times.

I personally don’t see the value here to pull in the same functionality directly into the applet - doubtful many people will be actively changing the time all the time.

Anyway - feel free to raise this with upstream - but I expect they will similarly need to be convinced as well.