Furnace bank broken

When you smelt multiple stacks of items in an auto smelter, XP gathers up in the furnaces. this also works in the education edition. the problem is that instead of removing one item and getting tons of XP after smelt a double chest full of let's say potatoes, we have to remove hundreds of items to get the same XP. I am pretty sure this is a bug as it doesn't happen in any other version of Minecraft.