Take an unsized case. Put Dacron fluff in it to support the bullet in the case at the right overall length.
Taper crimp it to your desired dimension. Tap the bullet firmly against the bench. Watch the bullet move.
Jacket material is hard enough that the taper crimp does not form a sharp edged abutment for the case mouth, and the bullet still moves.
Don’t look at the ring in the jacket and posit it does something by looking at it. Actually test the effect of the taper crimp itself by doing what I have suggested and then try to tell me about how effective it is. Fee free to try varying amounts of crimp.