No they are not the same thing. Design focuses on the structural while decorating focuses on style of spaces. The designer can handle decorating while the decorator can’t handle the design aspects.
The designer is meant to handle all aspects including the design of the space, including working with architects, and the decorator just handles the feel of the space. Which includes wallpaper, and accents. The designer can handle structural changes, while the decorator can not. Say for instance we have a Design change……the designer can handle it, and the decorator can not handle it.
The decorator is mainly there for the asthetics of a place.
The designer plans how a space is built, but the decorator plans how it will look when finished.