As much as Volksgrenadiers are portrayed as such in both games in reality they were wounded veterans and sometimes older soldiers equipped with stuff like the StG 44s to make up for their lack of numbers.
I don't think Germany was as stupid to give probably the best infantry weapons during the war to "juveniles and old men".
The volksgrenadier division was pretty messy. It was a mix of soldiers across the whole range. Juveniles and old men as well as experienced veterans and regular soldiers who were simply shifted to another division.
Also what Smartie said