Yeah, naming a song from a musical is like stating a tautology. Of course everyone associates the song with the (film of the) musical because the song was specifically written for the musical and is rarely performed outside of the musical.
There are some exceptions, of course, like the musicals Rock of Ages and Moulin Rouge that used pop songs.
And speaking of Baz Luhrmann films, I now associate Perhaps, Perhaps, Perhaps with Strictly Ballroom due to the great scene it's used in in that film.