In the latest snapshot, when creative mode music plays, switching your gamemode no longer stops the creative mode music playing, even when switching into survival mode (tested in a new superflat world).
This can cause creative mode music to play in survival mode.
I found that there was a bug report saying that the music shouldn't stop, but I also found a comment saying that it was working as intended.
Here are the links:
Do note that the tickets you mention are very old and the WAI resolution on them is probably no longer valid.
MC-131360 has been fixed recently, which indicates that this was an intentional change.