Thank you for a reasonable comment. To the best of my understanding the non-archival nodes will still need to download and process the entire block-lattice. Only then they end-up pruned.

BTW, another “fishy” thing is confirmation finality (instead of probability) design principle. One of the best inventions behind Bitcoin was specifically giving up on finality to embrace probability, which — when you think about it — is much more natural in a decentralized system.