I've copied tue same problem I'm having now from 2016. Have you fixed this yet? I see 150x150px previews....
Today I've installed the wpDiscuz plugin with the media uploader. I'm impressed with the responsiveness. The size however doesn't get determined like the video size settings (those are working). It always use the Wordpress thumbnail size of 150x150.
Is this expected behavior or not? I was expecting to set the size of a single image to 600x600 max and 300x300 for multiple images.
