Couldn't agree more - getting a TTL cable was life changing..
I've bricked ERX after trying to revert from OpenWRT snapshot to EdgeOS - and at that point getting the cable was the only option. The benefit is now I can play with flashing the ERX without any fear as there's always a TTL cable around.
On another note, I also had to get
initramfs-factory.TAR from the same source as you did - that was about a year ago.