This seems to have been introduced by https://gerrit.wikimedia.org/r/#/c/mediawiki/core/+/464768/ at line 497 of the new XmlDumpWriter.php code. The previous behavior is that the stubs should contain size but not content or the xml:space attribute for the text element; the content dumps should contain the xml:space attribute for the text element and no others.
Related Gerrit Patches:
|mediawiki/core : master||XmlDumpWriter: emit xml:space only if text is present.|
This looks good for stubs and page content dumps on deployment-prep; stubs now does not have the tag and page content dumps still do, which is what we want. Once this is deployed to all the wikis we can close the task.