I’m not sure any of this can really be generalised. Controlled efforts on roads or smooth trails aren’t really going to represent how fast you’ll get up a technical climb in race conditions. It doesn’t look at how open/closed or full sus/hardtail will respond to the big accelerations. There’s also going to be inherent bias from each of the guys making the video.
I’d wager that someone could perform the same experiment can come back with results showing that there is a difference between locked out and open.
Even the studies that Dylan quoted were so small that you’d need to question if the results are generalisable.
Interesting and fun, but a bit of Bro-Science if you ask me!