As mentioned in an answer here it should show "too old to migrate" on "off topic" flag of old questions otherwise someone could go on flagging lots of old questions that are/were off-topic only to find it useless because the questions aren't moved even though their flags are deemed helpful.
Do you have an example ?– user9517Aug 17, 2014 at 6:57
@Iain serverfault.com/questions/194567/…– laggingreflexAug 17, 2014 at 10:13
Doesn't appear on VTC anymore either.– Michael HamptonAug 17, 2014 at 20:50
Apparently this was silently (I can't find any announcement) changed sometime around March 2014.
Related mSE question complaining about the same (and "Very Low Quality" has disappeared in the Flag menu for upvoted posts): Tell me why a close or flag option has been disabled!