I think what most people miss in this discussion is how few opportunities there are to be an "assembler". The real work is in finishing the shell, then measuring it correctly for drilling. While it is possible to buy pre-finished, drilled shells, its very uncommon. So most people are buying raw shells.
Here's an example. I have shells hanging in my garage with 10+ coats of lacquer or oil finish, each coat sanded down before the next coat is applied. Once they're smooth enough and thick enough, I'll sand the shell 9 times in a row, progressing up to 2500 grit. Then I'll buff the shell with 3 different levels of compound. It took quite a while and lots of practice to figure out how to do this and get a glass-smooth finish, but I know how now. It's still a lot of work. Once that's done, I still have the opportunity to screw it up by measuring sloppily for all the holes (37 holes on an 8-lug drum). Then I could screw it up while routing the bearing edges on the finished, drilled shell. After all that I could screw it up while sanding in the snare beds by hand.
Everyone is welcome to their definition, but this feels to me like a lot more than simple "assembly".
$.02