Coal Ore in furnace

I don't understand the bug. Is it in the labels on the items? If so, please translate it into English.

No, why should the bearing burn to coal with coal?

That's what it has always done. This behavior is intended.

It’s intended to burn coal ore blocks to get coal items?

Yes. Sounds useless at first, but imagine adventure mode when you have no wood, some few coal, a lot of coal ore but no pickaxe to mine the coal core blocks, so you can gather additional coal.