Pent - you getting 3% from Google's dashboard? I don't know how they come up with those numbers, but I've found my stats to be much different than those numbers, usually WELL in favor of the newer versions of Android. Seems like they do themselves no favors by reporting the numbers they report, cause the reality seems MUCH better for them than their own numbers.
I have (or work on) several apps with (fairly) large audience:
500,000 active user app: 20% Nougat, 56% Marshmallow.
18,000 active user app: 27% Nougat, 58% Marshmallow
26,000 active user app: 16% Nougat, 47% Marshmallow
Bluetooth Tasker Plugin (low numbers): 35% Nougat, 43% Marshmallow.
Clearly, you are correct - Tasker users upgrade at a higher rate than others, but I promise you that the biggest app I mentioned does not have an unusually geeky audience, and it's at 20%, which is still well above 3%.