I find the key to running the 11 speed version of that cassette is to use a 12 speed chain on the 11 speed cassette. With the 12 speed cassette you're on even tighter tolerances.
I started to stare at the cassette and a 11s version, visually the base of the cogs on the alu block looks wider than the steel ones , this may explain the difference in spacing, tricky to measure with the tools i have available.
I guess i'll have to try it on a wheel to find out if it shifts OK