Yeah I don’t know what I expected - the latest ISO is up to date so I can’t reproduce it on that. That said, the latest Pamac definitely did fail on the older ISO - If someone wants to test on that ISO version, here’s a direct DL link: https://mirrors.xtom.com/osdn//storage/g/m/ma/manjaro/kde/20.0.3/manjaro-kde-20.0.3-200606-linux56.iso
I’ve marked the below answer as the solution to your question as it is by far the best answer you’ll get.
The bug in Pamac’s update still exists, it just doesn’t happen if you don’t run the update. Falav’s comment was just the solution to me testing on a later Manjaro release, not Pamac itself