The AG's own guidance back in 2016 allowed for already owned lowers to be finished into firearms, lowers that would not have had to be registered (in fact, many argue that even a lower built into a firearm doesn't need to be registered because no transaction took place).
As far as the 8/1/24 date goes, it doesn't say anything about registration - it says "lawfully possessed". So is a lower purchased between 2016 and 2024 considered "lawfully possessed" even though it has not been registered (which it couldn't have been, as the eFA10 doesn't have a provision for that)? Yes, because "copies of silicates" are grandfathered in under this bill.