My answer is based strictly on the numbers as your question has quite a few of them. Thus I think they interest you. I'm going to narrow down my answer even more by dealing with only color. Yes, 1/32 can make a BIG difference. How big would depend on the new blood and how close the new blood is to the old blood. For visualizing, think of paint. I love the color fire red. Always have. It is really really hard to get paint to be fire red. Once the formula comes out right, the paint people don't like changing anything about that fire red paint. But lets say some new paint company wanted their own special blend. Then sure they could take that fire red formula and add say 1/32 of white. Big difference. Now maybe 1/32 of brick red would not make as big of a difference but it would be different, not as vibrant to be exact.
I know paint is not the same as chickens but there are so many things breeders here are breeding for to match the standard, leg color, size ~ length, height, weight, feathers ~ how fast or slow they come in, the color, the size, even lacing. I'm sure there are other breeding qualities too. I'm thinking a breeder with some skill and experience could come up with 32 things to check on a bird. Now if this new blood messes with just one of those things, it can be hard to fix even if the breeder has a non mixed first generation bird that happens to be either fertile or laying still.
This is just my opinion but I can fully understand why breeders might be a touch bit cautious about mixing in new blood. Plus what are they to do with all of the mixed breed chickens say the 1/16 or 1/2 not HRIR. They sure can't eat them all. Also when mixing breeds it is not as easy as mixing paint. The chicks don't all come out the same. One might have the new legs while another has the new neck.