Taper Crimp vs Factory Crimp

[Bret]

I use the taper crimp for pistol/straight walled rounds & factory crimp for rifle/necked down rounds.

This is my thought too, so I'm not understanding the concept of using a taper crimp on a bottle necked rifle cartridge. For background, I'll start by saying that my belief is the purpose of taper crimping a straight walled pistol cartridge is to remove the remaining flare from the belling step. The purpose is not to help hold the bullet like a roll crimp or bottle necked cartridge factory crimp does. So, what does taper crimping a bottle necked rifle cartridge actually do? There is no belling of the case mouth, so there is no mouth flare to remove.