My Minecraft Windows Edition just updated to 1.13.0 and I can no longer smelt Stone to Smooth Stone in a Furnace with any fuel type, i.e. lava, coal, charcoal, wood if the Stone was smelted before 1.13.0.

The name appears the same but maybe some inheritance has changed or something? In any case the only Stone that will smelt in a Furnace now is Stone that has been smelted with version 1.13.0... not the previous version.

The new Stone will also not stack with the old Stone and vice versa.