Just my personal opinion and thoughts here – OK?
It does not surprise me that you could not find something as narrow as that about dry aging. Overall I’m not sure why the cows diet has much to do with aging the meat. On the other hand the meat we eat is muscle and the quantity and quality of the diet is what determines the amount of fat which develops in the animal plus the physical nature of how hard of a life it lead getting that food. In other words veal is very lean due to the short life span. Free range cows often are tougher, while feed lot beef is undoubtedly better.
What I would suggest is you research the comparison in grading etc between grass fed and feed lot fed beef – as the aging thereafter is going to have the same benefit regardless.