This obviated the need to copy a filesystem to a new disk's swap space and then use that to really install the system.
Thanks for the reminder. I don't remember if V7 on the PDP-11 used the swap space (but I don't think so). That said, I fairly sure that by BSD 4.1 the boot loader did, which I think is when that trick was first added to boot phase.
Again, it was all about trying to get rid of the special /stand version of things. Funny, history would move on and we come back to that idea with busybox 🤔