That does sound like something they may do to cheapen the box store brand. They all used to be iron. SS is fairly recent with all the new regulations. The SS insert sounds like a good idea and maybe enough as the water doesn't touch the outside.Water Worker: Malleable Iron connection (with stainless steel insert) vs stainless steel connection for Well-X-Trol. If somebody is handling one of these, check that connection with a magnet. Assuming that is non-magnetic stainless, that would be an easy difference verification.
Maybe I will take an extendable magnet to a display unit in a store.