Sorry to read you discovered this on your own but apps don't seem to use those settings. Why is a long discussion that won't fit here. HOWEVER there is a fix. Go get a Roku box and then it's some HDMI source which will work as you expected.
I have a LF58 series 42" smart TV, I can change settings (brightness, contrast, Truemotion, Dynamic Contrast) but the changes will only affect signals coming from external sources.
There is no way of turning off truemotion or Dynamic Contrast or anything at all for the built in Netflix. I hate Truemotion and Dynamic Contrast so it defeats the purpose of buying a Smart TV.
My model is the Latin American version, LG here says the only person that can see it is me so there is no issue.
Last Night I chatted with an US customer service saying I was in the US and my model was the American version, he checked and recognized the issue but he said he can only report issues for existing models in the US. What can I do?

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