Its different but I cant say that it offers much of an advantage.
What they offer is a loosely fitted sleeve that drops down to the base of the seating die then rides up with the bullet as you lower the press stroke.
When the sleeve tops out you begin to seat the bullet in the case neck.
If you study one of them you might come to the conclusion that the advantage is its simply a less expensive way to build and sell a seating die as all the die bodies can be machined the same between calibers.
Hornady does pretty much the same with their neck dies as they are sold by neck diameter not specific cartridge.
By that I mean a Hornady 25 caliber neck die does everything from 250 Savage to 25-06.
