Yeah, and I never argued that point. Pretty easy to find registered BH with minimal white, though. But, even if someone uses a BH bull or cow on a mongrel cow or bull, and gets a calf with too much white, that black calf will be worth more than a red one with too much white.
I've been the one arguing the point about excessive white as a reason to not use Hereford genetics be it red or black in a mixed herd.
You might find a Hereford traditional or black type that is conservatively marked I agree with that. Some traditional Hereford breeders have been selecting for conservative marked cattle with eye pigment, even red rings around the eyes, red legs, neck etc. May even be some red Angus slipped into them too to achieve that. Reality is that even though that a very conservative marked animal looks the part the hidden genetics behind him can come back to the forefront and be revealed in some of his calves.
I raised a purebred Hereford bull from both registered Hereford sire and dam. That mother of that bull was very conservatively marked with just a white face, red neck, red legs very little white on her belly. The bull calf had more white but normal for a Hereford. I used him on my mongrel cows as you call them some Herefords some F1 Angus Hereford crosses ie BWF. The results were all over the spectrum some conservative marked calves and some with much more white than either parent.
Some years the same mating would yield conservative marked on year and a lot of chrome the next.
The same thing was true with the mongrel 75% black Angus 25% Hereford bull that for a fact was those percentages as all his ancestors were of registered stock of their respective breeds until his true F1 dam, his sire was registered Angus.
If that very conservative marked bull being high percentage Angus was throwing chromed up calves from his 25% Hereford out of BWF cows I know good and well that high percentage Herefords even though they are black they are still going to likely throw some chrome from certain cows.
I can say from real world experiences that even though those chromed up BWF calves have black hides, they get sorted off and sell like Hereford Holstein crosses which they are not but it's what they are perceived to be and thus they will not bring any more than a red one they are all about the same.
The conservative marked black or red necked calves will outsell them.