It would be impossible to get the tire onto the wheel with the ring welded on. On single-piece rims, there has to be a drop center section to let the tire bead drop into that area while it is being pried over the rim. The center of a split ring wheel is straight- - - -no dropped center, and no way to get the tire on without removing one bead ring. Drop-center rims have to be larger diameter to clear the brake drums. A 22.5" tubeless tire on a drop-center rim is the same overall height as a straight-wheel 20" tire. The extra 2.5" of bead diameter in the tire helps it slide over the rim and into the dropped center section.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!