The F-STOP included in this leak, from my understanding, isn't Valve's prototype. It's just in-development fan-made game to try and replicate Valve's unreleased prototype.
Strong evidence that this is fan-made: there is Cave Johnson dialogue in the video [0]. F-STOP significantly predates Portal 2 and I presume the Cave Johnson character as well.
[0] https://www.youtube.com/watch?v=HboQWe3FYbg