I have looked into this a bit. I think this comes down to the snubbie factor and is part of the reason that the FBI went to federal 158 grain Ny-Lock for 38 and 357 snubbie revolvers. This ammo was specifically designed to have reliable expansion and penetration out of snubbies. If i remember correctly they found that 2" snubs simply did not generate enough FPS to reliably ensure consistent hp opening. Basically the bullet is to slow for Jacketed HP out of 2" snubbies. In their testing they tried faster powders but found while they got the speeds they needed they increased pressures to much. So they went with a combo of softer lead, with a protective jacket and a slightly faster powder. Giving something like 860 fps out of a 38spl 2".
It is what i carry in my wife's 642, I even load it in the 627 from time to time.
you can see it next to my wife's 642.
It is a super soft lead hp, jacketed in nylon. it is very accurate ammo, and opens quite reliably. There are a dozen or so video's doing the same test you have done on youtube. It comes in 2 flavors, 357 and 38spl. I typically only buy the 38 spl.