I spent a lot of time in all the groups. White is much slower then black when both groups are of equal size. Black is very experienced and have a lot of trust in the others driving in the group. Passes are given early and without hesitation. Generally it is fast and it does have the same issues as white when promotions from the lower group gets it’s newbies.
Black does get mixed with Red quite often from past experience mostly during club races or braiden events. The extended passing is a good learning and trusting time.
I am on the fence about the extended passing zones, I think yellow should be taught them early even though at most times only the red group really uses them. Yellow is aware and displayed ability to watch their mirrors and give passes. I also try and teach taking late passes with no one there so they can feel comfortable to deviate from the line and so they do not sling shot out back onto the line after the pass. This usually consists of having to take an inside entrance fast and then slow right down and stick to the inside results in a much slower exit speed then if you were on the line.
Anyways great question and great responses from both sides. Bottom line is there is a difference between these groups doesn’t matter the specific passing rules applied.