Honestly this argument is pointless. There are many OMS with an MD that never use it. The issue is not having an MD or not, the real issue is the lack of interest of many OMS in integrating themselves in the hospital setting. Unlike other surgical areas, as an OMS you can be in private and never step foot inside of a hospital. In ortho, neurosurgery, plastics, etc...the kinds of cases they do requires that they are part of a hospital and not isolate themself as most OMS have in private practice. What the field needs is not more OMS with MDs or fellowships, what it needs is more OMS who are willing to affiliate with teaching programs, and their local hospital taking trauma call. What's interesting is 5 out of the 6 attendings that won FEDA awards (Faculty Education Development Awards) do not have an MD, which goes to show that the future of OMS still lies with surgeons without MDs. Being that the majority of Chairs and PDs of OMS programs do not hold an MD is proof that the degree is not doing much for the specialty. The respect OMS has gained in hospitals did not happen from switching to MD tracks, it happend because of the pioneers (e.g., Fonseca, Ellis, Marx, Assael, Tucker, Haug, Kent, Block, Laskin, etc...) that were in the trenches and not abadoning their specialty to make $$$ in 100% private practice. So the take home message is MD or no-MD doesn't make a difference, what is the most important is what you make of your training and career. All the surgeons I listed above do not have an MD and I think its safe to say that most of us would be lucky to have half the skills they have and accomplish 10% of what they've accomplished.
I just wanted to add that one of the single degree pioneers you named has been my mentor and I have spent time with him. When I talked to him about programs, he strongly suggested getting the MD. He felt it was the way to go nowadays. He told me that unless you were already 40 when applying, there was no reason not to do the extra 2 years of an MD program.