TexasCHLforum.com

As reported, there are three curious exemptions. First, C&R (Type 03) FFLs don't have to go through this process, and neither do Type 06 (ammo manufacturers). I don't know why a 06 FFL would be shipping a firearm to a California FFL, but I suppose it's possible.

The third exemption (which isn't mentioned, so it might not be obvious) is for non-FFLs. The sender doesn't need a license for interstate transfers, only the recipient.