Not many seemed to care to click the link in that thread. If one did one would know that it was to a bug report and a fix was even posted in the same link. Screenshots work just fine.
The bug report was for not being able to screenshot in situations when it wasn't actually disabled.
The fundamental problem that the GP is referring to and that demonstrates the loss of control over one's own devices is that it _is_ possible for apps to disable making of screenshots to begin with.
I have written a far more extensive post just now on HN that fleshes out the overall argument against focusing on encryption - please read it here and we can discuss: