Scaffolding Blocks Break on the top Slab when they fall, they also cannot be placed on them

When I was building, I tried to put a scaffolding block on the top layer of a slab, it wasn't placed. I tried dropping it from 1 block up, it broke. It isn't the slab that touches a block below, it is the one that is at a block height without a lower slab. I'd like to know if this was meant to happen (I doubt it was) or it IS a bug. Thank you what whatever you can do.