Nope, Service Factor is a rating applied to motors that is multiplied by rated HorsePower to determine Brake HorsePower. Brake HorsePower is the amount of power the motor will produce before stopping.

Many inground pool pump manufacturers manipulate Service Factor and offer what is essentially the same pump with the same performance with two different HP ratings; one full-rated and one up-rated (or max-rated). This practice can make comparison harder, not exactly apples to oranges but apples to cored apples. Above ground pump makers don't seem to publish Service Factor rating at all - making comparison that much harder.

It makes sense to me to put in a smaller pump especially if your clean filter pressure is pretty high.