I have a leather pocket holster for my G42 that I carry in my strong-side cargo pocket. Drawing from a cargo pocket is no different than drawing from a flap holster - you gotta get the flap outta the way to get to the handgun. Given the floppy nature of the cargo pocket flap (and the fact that the pants themselves will ride up during the draw), presentation from the cargo pocket is definitely slower and more prone to slight fumbles than other forms of carry. Nevertheless, it's my preferred form of carry since it's the most comfortable and least obtrusive. My point is that I dunno that I'd fault the holster in the video for the presentation fumbles - it pretty much seems to be the Achilles heel of cargo pocket carry.
And, on a soapbox - reholstering a pocket gun with the holster in the pocket is an ND waiting to happen. Pull the holster out, insert gun, and put holster back in the pocket.