Hell, none of these pull-ups would count as (1) Marine Corps pull-up.
No kipping, over hand grip, full extension lock out at the bottom & chin needs to be clearly over the bar.
Try doing a pull-up with a monitor counting the reps. They will decide when the arms are at full extension & will tell you when to pull up. They then will only count the rep once the chin clears.
i wouldn't count one rep on any of these video's.
Geo is close, but the hammer grip has to go. Also, some of them there wasn't full extension.