Over the past couple months, I've noticed that the updating a world does not properly tell the API that it was updated. On multiple occasions, I have uploaded an update to my world but it didn't appear in the "Updated Recently" section, and the website had an out of date "Last Updated" date.
Strangely, updating twice within a short timeframe (a few hours) fixes this. I found this when I needed to apply a hotfix shortly after a major update. Both times I ended up doing this the world "updated" status was not changed until the second upload of the day.
It's worth noting that updating the description or title of a world via the website gives it the "Recently Updated" tag immediately, without needing to do so twice.