Doyle, you're quite right. The fact that the officers were petitioning Senator R. W. Johnson, Hindman's prewar political foe, on behalf of Shaver (a Hindman acolyte), says it all.
Later in the war, Shaver was in Tappan's brigade, and led the brigade when Tappan was temporarily in command of a demi-division. But Tappan's not being promoted blocked Shaver's promotion.