In my house, for a bedroom, the first light switch from the door, controls the overhead light.
The second switch from the door controls the overhead fan.
And the third light switch, if there is one, controls either sconce lights or the top of a receptacle so that a table lamp can come on.
It works that way in my house because that’s the way I did it.
but why would a switch that is the source of power for both lights but only supposed to be the switch for one, become the switch for the other?