site rotation is important especially when the muscle is being overloaded.
since aas is NOT site specific, i see no other advantage to pinning small muscle groups.
personally, and you do what you want, I start with the largest muscle groups
the glutes
you got, or at least you should have, two of them? when you feel you have overtaxed that muscle group, move down to the next muscle group
Quads
when you feel you are beginning to over tax your quads, move back up to your glutes.
I think you will find if you do this, there is no reason to pin a minor muscle group like bi's or calves.
I pin about 5ml into each glute. no issues. no pip.
something to think about...