Does GLSL flat modifier improve performance on Mali?

I got curious if flat modifier affect performance on Mali devices or not.
Doesn't matter if I put it into shader or not - result from Mali Offline Compiler is exactly the same.
In theory not doing interpolation might make things faster but I don't see any reduction in cycles.

Should I have it as potential optimization or not? 

I stumbled in some old report where it was even slower (on desktop PC using ANGLE emulation)