The oil pump is mechanical not electrical, so it makes zero difference what oil you put in. Your biggest limiting factor with mechanical oil pumps is the max amount of FLOW it can sustain, which since this is almost the same pump as in the OG K20 and K24, it can sustain any oil viscosity that has ever been used in the K series, so pretty much 10w40 and lower.
I run 5w30. I don't see why anyone wouldn't unless you live in permanently cold climates. The reason you want low viscocity oil is to get quicker flow to the turbo, but if its over 0 degree's C your flow between 0w20, 0w30, and 5w30 is so close at cold start it makes zero difference.
If you run e85 then you simply want to change the oil more often since ethanol is close to alcohol, which breaks down oils of any kinds.