He shouldn't need it with stainless. That's the whole idea. He sure did make a nice looking smoker though. Very nice.
I used T304 stainless tubing to build what are called rock sliders for my off road vehicle. The idea was so they would never to need paint or servicing. So far after about 10 years of rock crawling abuse, they are still just holding up just fine. Scratched, scarred and even dented here and there from all the abuse yes but still not one speck of rust.
Stainless is also much tougher and stronger than most other steel alloys in common use. It really takes a lot of force to bend the stuff, even the 2" OD, 0.120 wall stuff I used. I broke a bending die in a bender just bending up some 1.5" OD tubing. The only things to watch for are that the stuff is a bit harder to work with and it's getting really expensive to buy the materials. It's so expensive now I don't think I could afford to buy and use the small quantity the way I did before.
Aside from the toughness, it work hardens in an instant when you try drilling or cutting it. Although I found WD40 to be a good cutting lubricant for machining the stuff.
Also most of the flat stock has a grain that you have to pay close attention to when bending or it will crack. That is unless it has been normalized or annealed first. Of course annealed material would cost even more.
Stainless does however yield a much better finished product and it should easlily last a life time of normal use. However, I shutter to even think of what he built would cost if it were bought and sold commercially in the retail market. It would not be cheap but still well worth every last red cent of the price tag.