Beantown, I think it is more so just an ambigious situation for some.
Ninnis deserved an oppotunity to continue, and did a great job with Kubank. I think the concern is that scouting the globe for high level assistants might have the capacity to destablilse before even properly starting. There should be enough quality assistants in Australia already, and it is not necessary to seek these kind of assistants. Like many have also said, you have to question the motivation for international coaches to completely relocate to the other side of the world for an assistant role only, unless it was seen as a stepping stone. Most were questioning the idea of Joyce being here, and it seemed like Ninnis and Kubank were working well together.
In saying that though, coaches like Roth, Tatum, Maor all came to the league as assistants and were influential before going on the be successful head coaches.
Hopefully, the intention is to just surround Ninnis with some great assistants and that it works out for the best.