It's a bug but non breakable.
In the dokuwiki extension manager, your plugin is always proposed as updatable.
I think you will update plugin.info.txt file for each new merge as indicated in https://www.dokuwiki.org/plugin:extension
Updating an Extension
When you press “Update” the Extension Manager will use the Download URL as provided via the online repository for retrieving updates. The extension manager will re-download the extension and install it again, overwriting the older version.
For the update process to work properly it is necessary that the date “Last updated on” in the Dokuwiki Extension repository equals the date in the file plugin.info.txt for plugins and template.info.txt for templates in the source tarbal/zipfile. If this is not the case: the update will not take place or the “Update” signal persists.
If an extension is updated, the Extension Manager will remove all the files listed in the deleted.files file if such a file is added to the extension.
It's a bug but non breakable. In the dokuwiki extension manager, your plugin is always proposed as updatable. I think you will update plugin.info.txt file for each new merge as indicated in https://www.dokuwiki.org/plugin:extension