I understand your question in that you are asking why not get ODD for 2-73 in Front DM along with 3-71. Personally, with it being a small biotech, I wouldn't want to see it start stretching itself too thin. They should be focusing on the big money makers (like Alzheimer's).
Could it be done, sure. But I think major investors would be happier with separate focuses right now. I would also imagine that the approval process for 2-73 would be faster to get through after approval in Alzheimer's.
This is my uneducated opinion, but as an investor, let us focus on getting 2-73 approved so we can start making some revenues...