Export As is not WYSIWYG in colours.

I am working with multiple artboards in the same document. They use Gradient Fills adjusted to each by hands based on what I see on the screen. 
Using Export As gives me completely different result.The difference can be easily spotted on a screenshot.

I can assume the real issue is how Gradient Fill works. But still.. I m pretty sure export should be more respectful to what I see on my artboard.