I do agree with those who suggest that black soldiers were scattered and relatively few in number. If Cleburne's plan to intergrate blacks into the Rebel ranks in large numbers had been accepted when it was made instead of a year later, too late to matter, the CSA probably would have won.
The fact that the Confederate government rejected Cleburne's proposal in 63-64 shows that defending slavery was still a war aim. The decision to implement something like Ceburne's proposal in 64-65 equally shows that defending slavery was not their PARAMOUNT objective, as they were willing to abandon it when the alternative, defeat, was very clear and present. Like most of us from time to time, they postponed the decision that might have saved them uintil too late.