My guns, both modern and old, clean up easier when used with black powder. Every time I shoot heathen stuff, it takes a couple of black powder sessions before they get back to their easy cleaning ways. So, for me, it does make a difference.
FWIW, I find cleaning up after black powder shooting far easier than after shooting heathen smokeyless fad powder ammo. I think that if it were studied in depth that the "fact" that cleaning after shooting heathen powder is not necessary as often would be proven wrong. It's my educated guess that all guns shoot better with clean bores and actions. We just do that more often with black powder because of the corrosion boogyman. Maybe it's a good boogyman, huh?
DD-DLoS