Today, an extension that is bundled with XWiki Standard (and thus has no download button nor mention that is installable with extenion manager) has no explicit information about the fact that it will work on an instance of XWiki out of the box, without doing anything.
Thus, it may be confusing for a user looking up extensions for their usecase, and they may endup installing old deprecated extensions rather than using the standard XWiki features.
Since the store is called extensions.xwiki.org , the users navigating through it are probably not expecting to find on it things that are already available, they expect to have to do something in order to make it work (like an "add-on") so whenever an action button is not available they would assume the "extension" is not available.
For example, compare, in the attached screenshot, the display for the "display" macro vs. the "include" macro:
As improvements, we could
- at least have the same green box, with a message saying it's bundled / works out of the box, no action is needed
- drop the empty "compatibility" section which sends the wrong message being empty (as if there was no compatibility when it actually means that it's always compatible because always available)