It is protected by the VRA because it can be safely expected to be represented by the candidate of choice of its Black residents. That means it needs to remain that way. 50% has nothing to do with anything.
True, but that also means that drawing it to be 45% black probably works fine.
The problem is with challenges, and who drew the map. A map drawn by Dems to favor them would be less likely to be challenged if a district is only 45% black, especially if the reason was to help improve the performance of a neighboring district. Also, before
Bartlett last year, minority districts less than 50% were OK. Now they are permitted, but don't qualify as a section 2 district.
If the map is drawn by the GOP to favor them, a challenge from the Dems could easily be based on a failure to create a majority-minority district when such a district could exist. That's a key to a challenge under
Gingles, and the GOP is more likely to avoid that challenge by scrupulously making the districts over 50%. Since the GOP legislature is drawing the map to send to the Gov, I assume they would want to avoid a subsequent challenge in federal court from an external group.