Think of it this way too, a flowchart.
Is this an AR or copy/duplicate? If yes, was it registered before 7/20 (btw Healy said on or before 7/20, so this doesn’t even align with her guidance)? If yes, it’s not an assault weapon. 8/1 date is irrelevant. You don’t need the exemption.
If no, was it lawfully owned, registered, and serialized by 8/1? If it was a lower, it was lawfully owned and the registration requirement was met because there is no requirement to register it. If you built it and didn’t register it… then one could argue it was not lawfully possessed and it was not registered.
Not a lawyer. You have a week to figure out what to do.