Nothing wrong (or illegal) about it, Lee. If you've washed with commercial soap in recent memory, you've used soap with little or no superfat.
I would say that for most people most of the time, especially beginning soap makers, building in a little superfat is a good thing as insurance against making a lye heavy soap by mistake. That said, if you know what you're doing and want to try a low or zero superfat soap, why not? As long as the soap is zap free when it's used and is sufficiently mild to the skin, that's really all that counts.
Also, every online soap calc I've looked at so far makes an assumption that NaOH is 100% pure. That's seldom the case, so this assumption builds in a "hidden" superfat equal to the difference between the actual purity and the assumed 100% purity. My lye is about 95% pure, for example, so a "zero" superfat recipe if designed in Soap calc and made with my lye actually has 5% more superfat than what I intentionally build in.