When you visit the flathub.org website and click on “Updates,” it simply displays the most recently updated programs. But that’s not entirely true. If you click on one, you’ll see that the program hasn’t been updated in a long time. So why does the program appear as “Updated” when you click on the tile on the website? And for some, you can see that there was a recent update. Actually, those should be filtered out.
AFAIK, the updated does not mean released.
For example, every change to the manifest file would trigger a build, and that change might be trivial (a change in the metainfo/appdata file) or important (related to an application dependency).
In the end, these changes should be published to users, and thus, we need an update mechanism to reflect changes to users.
Some app authors don’t correctly add changelogs or updates are only packaging changes. Hover the “time ago” element and you will see, when it was build.
There is no flathub.com, it is flathub.org, I edited the OP because people will invariably click on it and be taken to some random spambot site later.