bf wrote:
.....

Bill, since he was making the back out of 3/4 ply, I don't think a
second stiffener on the back is necessary, if he attaches the shelves
to the back. Of course, if he prefers adjustable shelves, I agree with
your idea.

But, OP did specifical want adjustable shelves and was looking to avoid
the holes in the back being obvious if he used pins there as well as the
ends...