Actually the Tri-Triska had the back side of their blades sharpened as well so to slice a small hole in the skin before the blades open fully.

I know how all three of these heads operate and all three deploy their blades after they have entered into the animal. Two have or had their blades sharp so they would slice on their way in and one don't.

I can't find Tri-Triska's web site so they may not be around any more. I suspect a lack of advertising like the aftershock. Advertising is everything in the world of business.