Given that the content item has 3 translations - English, French, and German.
When I edit the content item in French and save

Then the new version of the draft will appear under the 'Draft under edit' table with Modified language as French

When I publish the draft
Then a newly published version is created and the modified language will be French.

To summarize, the language that shows up in the 'Modified language' column is always the language that the content item was modified in and not a list of all translations.