Its a shame this study missed so many opportunities to deliver more informative results.
As a thin, low birthweight, low muscle mass T2 I am quite interested in the role of skeletal muscle in the development of diabetes in later life.
My simplistic understanding is that muscle mass is an important factor in respect of how much visceral fat a person is likely to accumulate and visceral fat is an important factor in late onset T2. Simplistically, for a given diet, other things being equal, someone with a lower muscle mass will gain more visceral fat as a proportion of bodyweight than one with more muscle mass.
So I can easily believe that building muscle will be beneficial to BS control in T2 individuals.
I find it almost impossible to build muscle (low birth weight seems to be a limiting factor here) so my control is through LCHF diet and aerobic exercise.