See the page https://meta.wikimedia.org/w/index.php?title=Special:Translate&group=messagebundle-User%3AAmire80%2Ffuzzy+in+reverse&action=page&filter=&language=ru . This is the translation interface into Russian for https://meta.wikimedia.org/wiki/User:Amire80/fuzzy_in_reverse .

Here's how I got to the current situation:

1. I've created the bundle with all the messages saying "old 1/2/3/4" in English.
2. I translated everything into Russian.
3. I changed the message "three" to say "new 3" instead of "old 3".
4. I reloaded Special:Translate with that message.

What happens:

1. 1, 2, and 4 are marked with the yellow "outdated" badge.
2. 3 is not marked with the yellow "outdated" badge.
3. If you expand 1, 2, and 4, you see the yellow "This translation may need to be updated" note above the textarea, but no diff link (probably because nothing was updated in them).
4. If you expand 3, and wait until translation aids load, you see the yellow "This translation may need to be updated" note above the textarea even though you don't see the yellow "outdated" badge on the row, and you do see the diff link in the yellow bar.

What should happen:

1. 1, 2, and 4 must not be marked with the yellow "outdated" badge in the initial rows view on Special:Translate.
2. 3 must be marked with the yellow "outdated" badge in the initial rows view on Special:Translate.
3. If you expand 1, 2, and 4, you must not see the yellow "This translation may need to be updated" note above the textarea.
4. If you expand 3, and wait until translation aids load, you must see the yellow "This translation may need to be updated" note above the textarea even though you don't see the yellow "outdated" badge on the row, and see the diff link in the yellow bar.