I can’t tell if the background is a very clean real interior or a render, either way it makes no sense for it to be like that.
Everything about the scenes they used feels so intentional and designed its pretty ironic to have such obvious and weird flaw.
These are often two components stacked. There’s a cabinet box and a shelf unit. They may not have attached them if it’s a temporary backdrop just for this video. It’s also possible that the shelf is bolted to the wall, allowing the cabinet to slide underneath it.