"Set Unichest filters from adjacent inserters/miners" doesn't set Unichest content type

[plinfut]

I'm not sure whether this is a bug or a misunderstanding of this feature, but I thought this would set the Unichest filter to the filter of adjacent inserters. Like if an inserter filters only coal and leads into or out of a Unichest, dragging a rectangle around the Unichest after clicking this button, the Unichest is set to store coal. The content type of the Unichest is not set at all when I try this though.