The fact that blacks were indeed serving in actuality, in spite of the CSA congressional policy, just underlines how foolish the CSA congress was. Blacks were already serving, yet their refusal to acknowledge and expand on what was reality on the ground prevented them fro winning much desired foriegn recognition.
Despite the fact that it was already happening in practice, the CSA congressmen still up to 1865 maintained a "we don't see this this" attitude and still would not arrange for emancipation of those already serving them loyally. It is a complete denial of their own reality.
Had they embraced what was already in practice, they might have achieved Independence. Instead they chose to pretend that what was happening, wasn't.
To me that makes their final choices even more disgraeful, even more foolish. And congress wasn't alone to blame. As we have seen, even Davis denied a need until January 1865, saying on November 1864, theere is no problem, no need.
But since you mention historical revisionism, the greatest revisionism going on is the revisionism that despite all the first hand sources claiming otherwise, written first hand by Southern leaders themselves, those continous steady stream of documents saying for themselves that their main issue of secession was deeply rooted in slavery, and that the source of the war, the conflict of decades of political tension, was slavery. They were slave-holding states and they identified themselves firmly as such, were proud of it, said it openly, it was legal, Constututional, had made them rich, and they had no reason whatsoever to underplay it. They even stated continuosly is was God-ordained and biblically sanctioned.
But in our world slavery is repugnant. it is reprehensible to us that any human can be of no more importance than property. As so, the revisionist scrubbing is done, the contemporary words and reasons given by the CSA leadership themselves must be denied, purged, swept under the rug, cleansed, re-interpreted. That is the very definition of being "PC". The goal is to rewrite the reciepe of history and make it more palatable to modern tastes, therefore slavery's importance as an isue of deep devision is underplayed, it is now tariffs or taxes, or some other issue that just is barely if ever found in the actual documents themselves. "The states didn't secede over slavery, it was because they hated federalism" is the new PC revision. And the sudden emphasis on confederate blacks that you noted has jumped to the forefront suddenly simply is another tool to use in a deliberate attempt to prove that slavery wasn't THE issue, at all, that slavery was just some coincidence or side issue, that the real cause of contention was something else.
To do that successfully though, the very words and deeds of the CSA leadership has to be avoided or underplayed as much as possible. Even their final legislation, the bill refusing the guarantee of emancipation of slaves serving as soldiers was being mis-represented here in the forum to help further that new "understanding".