That is strange because some of our friends in California just ordered the lowers and did not need to do anything to get them. And some of them are ordering quite a few to bypass the July 1st serial number deal... BUT this is only for California, not the other 49 states???
"In July 2016, California passed AB 857 which requires all completed firearms to have a serial number applied by Jan 1, 2019. An 80% lower is not a firearm, so a serial number would only be required once the 80% lower is completed. Unfinished 80% lower receivers do not need a serial number. You may engrave a serial number of your choosing into your completed 80% lower prior to Jul 1, 2018. In other words, you can make up any serial number you want (as long as it meets ATF's definition of a serial number), engrave it on your receiver, and this will satisfy California’s legal requirement. After July, 2018, the law changes for the worse. If you build an 80% lower after July 1, 2018, you must FIRST apply to the California DOJ for a serial number, pay a fee, and they will then assign a serial number that you must apply to your firearm. In this case, you can’t choose your own serial number. If you build an 80% lower and use your own “unregistered" serial number after July 2018, it would be a misdemeanor.