I'd be interested in any differences in the pattern on the sides of the jugs, as well as any photos you have of the base. Differences in the base treatment don't necessarily prove that they're different patterns - but it does go to some way to prove that Crown made the pattern. Crown may have altered the mould to give the ridges in the base. In the EAPG books I've seen, it never has a lid, so they may have changed it to fit one - but we need an EAPG expert to check.
The name 'Owl and Feather' seems to be locally coined - certainly it doesn't seem to have the same name in the US. I would be cautious about separating them out as different patterns until the providence is known.
About Etherden, they were definitely Australian, and probably Sydney-based, but there's nothing about them in the National Archives anywhere in Australia, nor any other archives that I've searched, and nor have I come across any ads in archived papers and magazines. Maybe something will turn up someday.
Would it be okay for us to split this section out to attract people knowledgeable about EAPG?