It makes sense that the mob chunks which are harder to obtain, ie wither, to be able to used in the crafting recipes for lower tiered ones. after smelting them in a furnace of course

Or you can just get the correct tier chunks.

@blarghhh or you could add a recipe to downgrade them. There's this thing called crafttweaker. Use it.
hope this doesn't reopen the issue. I forget whether commenting on a closed issue reopens it. If it does, sorry