Calif legal lowers are not a "loophole" , although the gun grabbers will call it that.
The CAlif DOJ does not have certain AR/AK lowers listed in the AW ban, however SB23 "evil features ban" still applies. If you get a non-list reciever, you must put a fixed 10 round mag in it. (until they add it to the AW list).
When the DOJ adds these models to the offical list, they become mandatory AW and owners can register them or remove them from the state. If they are registed AW, then the owners can add "evil features" (ie pistol grip, det mag)
The CA DOJ has known about this for several months and have not added the non-list recievers to the AW list, therefore they are legal, and there are letters from the DOJ that says they are legal.
However, the DOJ is planning to update the AW list soon, so this won't last long.