this just goes to show ya that when a man knows what he's doing he can even make MDF look good. Very nice job, good idea, good workmanship, and very nicely done video.
When I make MDF arcade cabinets, I coat the cut surfaces with 5 parts water to 1 part wood glue with a foam brush. Wait about 40 min and sand the cut edge with 220 grit and it's hard as a rock and doesn't soak finish. Edited for correct recipe. Love this build.
It's very difficult to clean every bit of faull smell and du mpnes from any kind of wood and any pent or varnish you will try does nothing in the long run I have sad experience of. 60. years . ..
I'm guessing f it were elevated there wouldn't be enough space for the cat to "jump out" of the litter box, then exit through the enclosure door easily depending on the size of the cat.