Solved
Video Explanation Typically the Change-Over regs have the flare fitting and the single inlet regs have the NPT,
It's the first thing this guy explains...
The change-over ones seem to have a brass adapter screwed into the regulator, and it is the brass adapter that has the flare fitting, not the regulator. I suspect that the regulator has a 1/4 NPT on all types and the change over has the brass flare fittings installed so they use flare hoses, would taking the fitting out make it wok with an NPT hose? This is not my issue, but I just wonder this now... Guy above mentioned an adapter and was this the adapter?