Well, since you haven't started medical school yet, I can't expect you to understand. If you were an MS-1 or above asking this, I'd bop you on the head just for asking, but since you are MS-0, I forgive you.
The reason why it's a ridiculous proposal is because the only significant difference in curriculum between the MD and DO degree is around 2-3 hrs of OMM lab and 1-2 hrs of OMM lecture per week for two years. There may be some differences in emphasis, but the curriculum is essentially identical, besides the OMM. Therefore, having a dual degree program would be dumb. There's no reason to have it on a practical level since either one is sufficient to be a physician and essentially teach the same things, w/ the exception of OMM. Why would you want to add an extra year for no reason? You are a physician either way you go.