Every update had been reinstalling archlinux-keyring and the platform keyrings, and that reinstall ran the package's trust update again. The merged update asks pacman to skip a package that is already current. David Heinemeier Hansson said that reinstall was about 2s per update, more on a slower machine.

The pull request says a repository entry is keyed by version, so new or revoked keys still arrive as a new package version, and the skip does not drop that version. The keyring step still syncs before the main upgrade. David Heinemeier Hansson opened and merged the change.