I also think it’s like crawling vs. sitting in a planche. Extending is like strength-endurance training, I guess. It would probably work wonders combined with manual stretching.
I also believe most guys who’ve gained from hanging had some swinging involved.
IIRC even Bib mentioned to someone earlier this year that he should probably swing the weights if he doesn’t gain from what he was currently doing, I think he was doing BTC/SD only, he even hated on Bib for ONLY mentioning this. I would also have to guess that there’s not much else to it, since we all seem to come to this same conclusion, dynamic stretching is better than static.
Of course both dynamic and static are necessary for optimal gains, right?