OH, and I just saw this...so this is reasonable
https://www.cnn.com/2023/08/08/politics/supreme-court-ghost-guns/index.html
Ghost guns are not a significant player in crime stats per my previous understanding. However, anyone with sense would grasp that circumventing the registration data would make owning one legally in a state where you need a license very difficult. If the license required you to identify each firearm you own.