Given that use GenServer calls for the injection of the AST constructed in the __using__ function of GenServer, and given that this call is typically placed quite early in the module, and there doesn’t seem to be obvious deferment of this call, why can I override the behaviour callbacks with my own implementations?

I understand that module level expressions are evaluated before macro expansion, but def is a macro, so I’m still a bit unclear here.

EDIT: Sorry just to clarify, I conflated behaviours and use, I’m updating in the main post so that future posted are not perturbed by this error on my part.