Probably designed to be California compliant, which is naturally why California doesn't like it, because they want to get rid of AR-15s entirely rather than just have versions that actually comply their asinine laws.
It's an *extremely* smart-ass workaround because it installs a fixed ten-round magazine which cannot be easily detached from the weapon...it's just that the gun doesn't actually fire rounds from this magazine. This is literally sticking a stack of .22 LR bullets in the handle of the AR-15 and saying that counts as the gun's magazine for legal purposes, as opposed to the normal detachable magazine that the firearm actually feeds from.