From my experience this is BS. One local supplier (Airgas) here tells me this same line. One down the road (Matheson) sells me the same big bottle the last guy told me i couldn’t own.I don't remember the cut off but up to a certain size you can own and exchange. At some point they decided bigger bottles you have to rent and exchange. In both instances the weld shop will only exchange their own branded bottles. Of course, there's lots of large tanks in the wild that people own, and shady places that will fill for you as long as it passes recert. In my area there's a guy in a van (down by the river) that will provide this service.