:-) Depending how they used the Music Brainz data could be – there are enough longer songs around on albums at least. (Though American Pie was actually published as a double-sided single, interesting)

While this is admittedly rather handwawy, even outside of this I have the impression that there must have been some lengthening: It feels like basically every Rock & Roll song from the 50s/early 60s mostly is around the two minute mark and very rarely even approaches three minutes. Afterwards however, three or four minutes doesn't seem that unusual to encounter, never mind those really long songs, too.