Sorting Groups and AlphaTest Queue

I'm having an issue where sprite sorting stops working when I apply a sorting group to a parent object. The docs say "To sort Renderers within a Sorting Group, Unity uses the individual sort settings of the Renderers in the Sorting Group.". I take this to mean that each renderer within the sorting group will be sorted according to their "Sorting Layer" and "Order in Layer".

I believe I've narrowed the cause of this issue down to the fact that the materials being used are in the "AlphaTest" queue and not the "Transparent" queue. When I switch these materials to use the "Transparent" queue, sorting starts working properly, but then I lose the shadows those materials were receiving.

From what I can tell, Unity is falling back to its internal tiebreaker when using the "AlphaTest" queue.

Anyone familiar with a way to use Sorting Groups + the AlphaTest queue and keep sorting working as expected? I've searched but can't find anything that addresses Sorting Groups and AlphaTest at the same time.