It was a variant of the AR-15 because it was based off of the AR-15 receiver.
It also had a potential safety issue. An AR-15 was not designed to be a pump action, it was designed to be a semi-auto/auto. When you release the bolt on a semi-suto, it pushes the round into the chamber and closes on it. All is good. However, when you try and make it a pump action by just connecting the pump mechanism to the bolt carrier, you create the possibility (and high likelihood) of short stroking it, knocking a round into the chamber (without the extractor catching it), then stroking again and pushing the next round right into the back of the first round. Imagine the consequences of a nice pointy FMJ bullet being driven into the primer of a round already in the chamber... While its possible to do that with a semi-auto system, it's much less likely. And the bullet would probably hit the edge of the rim initially and cause a jam. It would in the pump action as well, but due to the nature of a pump action, the user is more likely to try to coax/force the round into the chamber (jiggling the pump mechanism, etc...) rather than clearing the jam.