Got the DLC today and was testing numbers. I noticed that while the Onna-Musha gets the buff icon that says +15% damage for cavalry from the Uma Bannerman, and gets a buff glow aura, its damage is not actually improved. Here’s a with and without comparison:
In both cases the (fully upgraded) damage is 19. Now I thought this could be a visual bug, but testing other units like Horsemen the damage does change (from 17 to 20). I also tested damage against a boar – the damage is the same with or without a bannerman. And to be thorough I checked with the Yumi Bannermen, who of course doesn’t work as expected since they’re for ranged infantry. As-is, Onna-Musha cannot be buffed by any type of banner. I assume some sort of oversight like the buff only improving melee damage and so the Onna-Musha does not benefit.
I found two other threads about this but they’re from December so I thought it was worth reporting again with current evidence.