[Q] Why is operation of a kernel different?

I use "Multi user app share".
This app rewrite "/data/system/users/10/package-restrictions.xml"

At first,
this file's permission, user, group are
660,system,sytem

when I have used this app,
In the case of CM10.1 kernel,
this file's permission, user, group are
660,system,sytem

Bad, In the case of dorimanX kernel,
this file's permission, user, group are
600,root,root

why?