It's probably not that different from rangefinder style cameras[1]. I don't think the problem with this one is with its transparent viewfinder, it's more that its output quality just aren't that great according to someone who tried it[2]. Seems like a neat toy at $45 though.

[1] https://en.wikipedia.org/wiki/Rangefinder_camera

[2] https://www.reddit.com/r/Godox/comments/1urlp8u/first_test_s...