Actually looks stronger than some "store bought" sheds I've seen installed.
There is half-moon steel shed (ie round top) that uses bunch of "trusses" (ie 16" OC) which are really just shaped round poles that later are skinned, once skeleton is done. A light storm of say 50 or 60 mph winds tore that thing to pieces in storm that went through Attica, KS a couple years ago.
Square tubing is awful stout once it's all welded together. Would be interested to see what all parts of country use this build method??