OK now I can see the reason!
In addition to lines:
ResX=5040
ResY=1050
we must change:
UserSelectedResolution=False to UserSelectedResolution=True
Do you add just this two lines by your self? And if so where from do you know that exept resolution we must add something else? I am asking to future knowledge of .ini tweaking. Is this option is necessary to all games on U3 Engine?
I really didnt read it anywhere! I either noticed it myself (its common setting on Unreal engine games) or the game had it preset in my case.