That’s shorthand for taking a three dimensional perspective to a 2 dimensional one. Or turn a v into an l if you just break it down. Look at it from this different perspective. I love flatpack design and have included it before now in a make-a-(green) plan post.
This is a whole apartment concept via Treehugger called 90 degrees by Dutch designer Louwrien Kaptein. This takes a drop leaf table concept on an adventure.