Hi Anthony,
True, Seostris' kiosk it can't be. But what then?
I tried googleing quickly and only found "White Chapels" seemingly being the main temple in each nome. But.... I can't find anything like it in my books. Not a word. And since the site was Touregypt, I'm not too sure about that. This could be a budgery. They use too much outdated material to be, IMO, really reliable. Shame really. This said, I can't find the White Shrine or Chapel in Budge, either.
It can't be a link to the Great White, either, because it dos not fit into the idea of heb sed. IMO.
Hah! Yes! But what it can be is the Nekhen Horus sancturay! White was the heraldig colour of the Upper Egypt, wasn't it. Moreover, these sanctuaries were very important in the sed context. "The row of Upper Egyptian sanctuaries", indeed. Maybe calling it the White Shrine instead of Pr-wr underlines the Upper and Lower Egypts being re-united here.
Maybe.
Ritva