Obliterator fails to convert multiple types of trophies into coal at one time

I noticed that I wasn't getting as much coal as I should have for 1:1 trophy:coal in the obliterator, when I would just dump all excess trophies in there at once. So I tested a few things.

1 boar trophy gave 1 coal

1 deer trophy gave 1 coal

1 boar + 1 boar = 2 coal

4 deer in a single stack = 4 coal

1 boar + 1 deer = 1 coal

1 greydwarf + 1 GD shaman + 1 boar = 1 coal

So it appears, to me at least, that it doesn't handle different trophy types at once. Going to submit a bug report, but thought I'd post this finding for now. EDIT: already a bug reported for this and they replied in July they will look into it.

edit: another configuration – 2 GD brute + 1 GD = 2 coal .. I was curious if the order they were in there mattered, and yes it seems so. The stack of 2 GDbrute was in the left-most slot, single GD to the right of it.