This is good news, but remember, it only applies to the lower receiver blank. The upper receiver components (barrel, barrel extension, bolt and bolt carrier) must still be made of gun steel. (Carpenter 158 for the bolt and bolt carrier, 4150 for the barrel) The fire control groups parts are case hardened forged steel, but the upper receiver itself can be polymer or aluminum.
Those are considered parts though and not subject to regulation.
mark
Even the dinosaur brained liberal politicians will eventually figure that out and make it illegal to buy, sell, manufacture or possess the parts. Like it will be possible to control that, but they’ll make a few high profile cases to make it look like the laws work.