Did Michigan become significantly smaller on defense, apart from injuries, youth and scheme?
I don't think this is what Carr was saying. I think he was factoring in injuries, youth and scheme and more stating size as a factor in the losing. He was commenting on the players that were on the field independent of those factors Maybe age was the reason for the lack of size like you say, but that doesn't make his statement incorrect.
Further, you show an end of season size difference of 16 lbs per starting player. Is that correct? If so, I think giving up 16 lbs to the man is substantial. I also don't think the WC for CG substitution makes sense. I think part of the point was that the scheme dictates smaller players being on the field.