With the provided instructions, even though 5.3.3 is 'available' in the repos, only 5.3.1 is installed, and won't upgrade.
Whatever is in the 'latest' doesn't update properly on server side.
If I edit the .repo file which includes 5.3.1, and change it to e.g. 5.3.2, dnf sees the updates and upgrades.
Something is wrong...