Maybe I’m just a bit too bony between the ears, but I have split several batches of beer between two different yeasts and always wind up with different final gravities. If CBC-1 would have fermented a wort to a lower FG than the yeast which was used, wouldn’t it attenuate out the sugars it would have had it been the original pitch, plus consume whatever is added for prime?
The business about better settling out in the bottle sounds familiar.