The replaceable pin is a good idea. The problem is that the breaker itself works well on new chains but bends this pin on a rusty chain. On the breaker, there are 2 places to place the chain but the supports for each are the same level. There should be a support for the outer link and a higher support for the inner link at both places. With a new chain, the link pin slides out with no problem being supported by the outer link on one side and the length of the chain on the other. But with a rusty chain, the chain pin takes more force which angles the chain as the inner link is not supported. This in turn bends the breaker pin which is not hardened.
I am having to use my motorcycle breaker breaker which I ground down the hardened pin to fit bicycle chains but it does not have the nice holder so you have to be careful to center where the chain pin is pushed to.
Answer. If they would harden this pin, I think it would also handle rusty chains too. If not doing that, they should modify the breaker so the seat for the chain supports both the outer link AND the inner link.
Buy these now and keep them in your tool box for that next d'oh moment.
If you aren't careful with your Park Tool chain rivet extractors, you will bend or break the pins. Replacement pins beat having to buy a whole new tool every time. Buy these now and keep them in your tool box for that next d'oh moment on a weekend when the nearest shop is closed.