Maybe they were for thicker woods where you cut half way with the regular blades and then finish the cut from the other side with the upside down blades...
Actually, I have a saw blade for my Saws-All that has teeth pointed away,,, It is for Drywall, has a pointed tip and you can plunge cut then cut out a hole... Yes It will fight you on the start.
Bosch used to, and maybe still does, demonstrate the quality of their blades like this. They put a blade in the jig saw then slam the saw straight into the wood and make the cut. It was pretty impressive.