This question came up in an edit. There are, unfortunately, many examples of both in the DB, so I’d like to see if there’s a consensus on how it should be.
If it is a consensus that these phrases are subtitles, or ETI, I’d like to request that the Soundtrack style guideline be updated to specifically say so, one way or the other. The editor that prompted this thread continues to add the phrases in the format of ETI, after several votes going against him, and after being asked by the Style Leader to follow the guidelines. But if the guidelines fail to explicitly state the decision, I don’t think he’s going to stop.
All it needs are a couple of examples quoted. Maybe also add one to the subtitle page too.
Problem is the online shops are starting to put this stuff into brackets which is causing part of the confusion. A subtitle colon looks so much neater anyway.