"So you don't reduce the impact force - you increase it. As you say in your second statement."
This is of course is true but how the impact is absorbed is important.
I attended a short course at Martin Baker many years ago. From memory they were giving a total ejection force of up to 15 G. Not many pilots survived ejection without serious injury to the spine during the early years of development. They had eventually discovered that it is not only the total G that is encountered (to a limit) but the rate it is sustained was crucial. They eventually incorporated a clockwork mechanism within the seat that, through series of stages, delayed the total G over approximately 2-3 seconds maybe less (I'm working from memory). This was from pulling the handle through to the chute being deployed. This very short period was sufficient to avoid serious injury.