(Slight) Goof

WTF? Lol
I don't think you understand what you're saying.
So WHAT? There's no goof.
Why can't a movie use an older song in it's trailer or in the film itself?

The 2009 movie Wild Hogs uses the song Born to Be Wild that was released in 1968.
So?

So you're saying if a movie takes place in 1990 then the songs they use have to be songs that came out in 1990?
Not before that?

A goof might be if there was a scene in the film where the characters are listening to the radio and the song "Shadows" comes on and one of the characters says "Wow I love this BRAND NEW song" - But otherwise why couldn't they be listening to a song on the radio that came out 6 years earlier??

A REAL Goof would be if characters from 1990 wre listening to a song that was released AFTER 1990.
See??

If you put on a popular pop music radio channel right now would you find it weird or a goof if the song "Sexy Back" by Justin Timberlake came on? NO not at all. But it came out almost 5 years ago.

I think you're confused Paul

Well now... I can say categorically that "Shadows" was not off all SA radio playlists in 1990, I used to hear it all the time. In fact I heard it on the radio a week or so ago, so it is still on some SA radio playlists.