On the latest Black Widow posters issued to cinemas, Desplats name is credited, not Balfe. I don't know if this is a misprint, or whether things have changed again.
Maybe this means both Balfe and Desplat have recorded their scores. It reminds me of the Suicide Squad situation where according to HybridSoldier both Steven Price and Tom Holkenborg wrote and recorded a score. They chose Price's score because it scored better with test audiences. It's possible that the same thing happened in the case of Black Widow, which is now going to be released in May 2021, apparently.