There's apparently prior art going back nearly 30 years. I actually discovered GF smokers here.I would like to think so, if a company were to challenge it / them. I did not know about gravity fed smokers until Masterbuilt, but then found the others through research. Some have fan addon's but most just a ball valve to control temps.
If you really want to pick nits...... is the whole concept of a gravity fed really non-obvious? It's big "secret" is that the charcoal column has to be completely sealed, and nothing more. I'm far from a fabricator, a design engineer, etc., I'm an IT nerd, and I'm able to follow it, and build one. It's not like a new sort of hydraulic motor, a novel method of chemical processing or some such.