Thanks Ted, I really see what you mean. There is a different feeling of nagareru in places. I always have a hard time evaluating steel color, I am sure it would be much clearer when compared against another sword to see if there is more of a whiteness in the steel. It is also interesting to look at the boshi in this tachi. While the sword overall does not have nijuba, there is a strand of nie floating above the boshi which is crisp and bright like a line of kinsuji which has floated above the hamon. This is only visible on one side.
As far at the nie activities in the ji, they seem independent of the kitae. The nie utsuri does not follow along with the pattern of forging, but rises and falls like a midare utsuri. I really need to scan the photo from the Juyo Nado Zufu, which shows this well (or if someone had volume 49 handy, they should be able to see this piece).
I have a tanto which also had this same dual attribution. It was originally papered by Kotoken Kajihara to Rai Kunitoshi in older polish. The sword was evaluated at the NBTHK, who said it was a high quality Yamashiro sword and should go Juyo to a Rai smith. After polish the sword received Tokubetsu Hozon to Enju (and will not paper higher). I can see easily in this sword why the attribution went to Enju. There is full length nijuba on each side, very similar to the Awataguchi Kuniyoshi tanto in the beginning Rai show catalog. Other Enju I have seen are very similar. The hada is more itame nagare compared with the tachi, but I think this is due to the steel being less healthy by comparison..