The cut copper stairs can't be positioned with the "fill" command such as other stair blocks, for example with the diorite stairs the command you must use to place a upside down diorite stair is " /fill ~~~ ~~~ diorite_stairs 5" which isn't posible with the cut copper stairs, for example I tried to use "/fill ~~~ ~~~ cut_copper_stairs 5" which places a normal stair from cut copper