Larry, I think what is difficult to build knowledge on is the slippery slope that gets us to where we're going.
As you indicated, today's modern Shiro's were RE-invented from Showa
at the time that they were being beni strengthened from Kohaku. Today's modern showa have been sumi strengthened by the addition of Sanke.
In mixing up the lines, different breeders using different keito, I don't think it's possible to get a clear picture of expectation.
Omosako in interviews published earlier with KB indicated he sees 5 different kinds of developing sumi. he was criticised as a breeder for having smaller koi that could not compete for size with gosanke. ( no criticism about quality tho ) So since that time he has sought and acquired and bred a bigger growing line to cross over into his own. I quess my point is that each breeder sees his results differently than another and their own vision of where they want to go with it has them constantly changing the direction and genetics.
What has always fascinated me is how the same water source among two different owners only miles apart can give such different results. I quess we see that in the mud ponds of japan, where some develop sumi or beni better than the other. All of these variables among conditions and genetics make it a tuff nut to crack. Still, we as koi keepers like the breeders we admire must search for answers within our own vision and resources and capabilities.
That said, it is often said of this hobby that we should not focus on the destination but enjoy the journey. So, as always it's fun to add new fish to our collection and to try and learn what they are telling us about our ability as a water/Koi keeper. I end my thoughts this way because the genetics is the breeder's job, the water keeping is ours. My problem is the more i learn of it the more I realize i have to learn.