I'm just going to chock it up to plot device for the reason I listed above. I think it was supposed to be a point of pain for Snake seeing someone he could have spent his life with end up with someone so closely resembling him. Like, maybe if he wasn't fated to be this messed up hero he could have had that life. But instead he's old and scarred, physically and emotionally.
I dig it. I'm glad I asked as that is at least head-canon now.
Edit: I guffawed at your picture and forgot to mention it. The people deserve to know.