Unfortunately, they can't just hide parts in that asset. I use it in my game and if I could go back in time, I wouldn't have picked it. It's overly complicated and too many things are tied together. For example, if you try to hide a wall, you end up hiding like half the scene. Also, they did weird shit like instance the taps in the bathroom, and tie them in with stuff from the bathroom. So if you try and hide the bathroom (which almost nobody uses in this asset because it's a badly done bathroom) you end up losing the taps in the kitchen.
The cutout opacity works though and so does the Iray camera. I have several variations of this asset saved with various parts removed.