Why are the teeth on this blade reversed from all other jig saw blades that are seen?

The jig saw blade (model #75-312M) with reversed teeth, is designed as a countertop/laminate downcutting blade. The blade is designed to cut on the downstroke rather than on the upstroke to reduce the splintering of material.

Additionally, whenever you cut with a jig saw blade, the surface where the teeth enter the material (typically the underside) is left with finer splinters than the surface where the teeth exit the material. Most users will turn the material over to ensure that the best finish is on the surface of the material. However, in cases where the material cannot be flipped over, a downcutting blade is required.