Hi , On AEM CaaS - version is not created for both page and assets on editing the metadata.
Although for page metadata editing, it does shows that page status is modified and in the timeline that the page was edited but the version still doesn't get created. In timelines there's a drop down which is 'Show all ' by default .Change it to 'versions' and you'll see no versions are created but changes are logged .
In case of assets on cloud , the version and timeline does get created only if you edit the binary by clicking (e) instead of metadata.The asset state also does not show modified even if metadata changes .
I guess if you have such a requirement of tracking any change in metadata, it might be custom on the change of metadata node. Alternatively , You may want to check by enabling metadata write back (which is disabled by default in cloud ) to see if that helps and logs history in timeline.https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/assets/admin/xmp-metadata.html?lang=en#enable-xmp-writeback
Note : Check with client if they are okay to write all metadata back in the binary as some data may be sensitive. Also, you may not want to add this extra processing step unless really required by the business.