Jim I do not like this niche and do not like the Schluter System's approach to any of it. I do however like the European system that Schluter offers up and do like the products from Ardex like Ardex 8+9 for fixing the short comings of a thin-set and Kerdi Band approach.
I will follow a system for sure. My system.
Here is the second Kerdi Board Niche installed with a scratch coat of Mapei's Grani Rapid on the wall. Still have not fixed the missing pre-slope but will get to that this week.
These walls will get Kerdi and then for safety and because I have never trusted Kerdi with dry-set thinset as a waterproof connection it will get Ardex 8+9 as well.
This niche set up like a tank with the spraf foam step behind it. Much stronger than I thought.