Steps to reproduce the issue

• Create Joomla article
• Add Tag

Expected result

• A) New row (e.g. id 43) in database table #__assets with name com_content.article.X (X = id of article) created.
• B) New row (e.g. id 44) in database table #__assets with name #__ucm_content.X (X = id of article) created.
• C) In database table #__content a new row with id X (article id) is created and asset_id has row value of A (e.g. id 43)
• D) In database table #__ucm_content a new row with core_content_id X (article ID) is created and asset_id has row value of B (e.g. id 44)

Actual result

• A) New row (e.g. id 43) in database table #__assets with name com_content.article.X (X = id of article) created.
• B) New row (e.g. id 44) in database table #__assets with name #__ucm_content.X (X = id of article) created.
• C) In database table #__content a new row with id X (article id) is created and asset_id has row value of A (e.g. id 43)
• D) In database table #__ucm_content a new row with core_content_id X (article ID) is created and asset_id has row value of A (e.g. id 43)

So the new row in #__content and #__ucm_content both link to the same asset_id and the #__ucm_content.X asset has no relation in other tables. This is not correct.

Additional comments

This behavior is introduced with PR #39165 which sets the flag $this->_trackAssets = false; for the UCM content table. This indeed reduces useless assets rows. However this change did not take into account the fact that a new UCM content row is created when tags are added.

The incorrect asset_id store is also mentioned in the comment of the PR: #39165 (comment)

As long as data is created in the #__ucm_content the $this->_trackAssets = false; should be removed. Or the asset_id in #__ucm_content should not be set at all and the column can be removed as the asset for #__ucm_content does nothing.