Not necessarily. The sound jack on a laptop isnt the same as it is on a desktop or tower. The sound jack can be located on the other side of the laptop where the mother board and other components are not located.
So this would result in there having to be some sort of switch that is hit when inserting the jack at that point. Which i can honestly say i have not come across in my time that i know of. So there should be something with the drivers that recognize that there is something plugged into the jack and cuts the sound to the speakers.