I don't think I can agree with that. GitHub's success, IMO, seems to be based almost entirely on its openness. It has turned contributing to open source software into a drop-dead easy task, which would never be found nor contributed to if they weren't open. And they keep making it easier. I've fixed a number of things with machines which don't have Git installed, simply because they have their on-site editor.
Imagine if GitHub were behind a paywall. Do you think it would still be the success it is today? And, I may be weird, but I very rarely look at the names associated with commit histories. The code should speak for itself.
The rest of it sounds about right, scientific publishing as a whole is massively backwards compared to GitHub, if you're looking at it from an "Open" perspective. But I think that a lot of that is that the researchers tend to be insular compared to the implementers (businesses guarding their IP aside - they're not really GitHub's target audience anyway). GitHub isn't used exclusively for comp-sci researchers to post their findings with code, it's more for people doing things with ideas others have contributed to.
There are experiments on GitHub, absolutely. I have a few myself. But the main thing that GitHub has done is to make final products easy to find, modify, and contribute to. I have significant doubts that it would fit a research workflow smoothly, without becoming something else entirely.