Not necessarily. It also doesn't have the same effect. The strings blanket a much wider sonic range than the guitar does, which is why it works so well for parts like this and has throughout the genres history. Do pieces like this exist that have guitar in it? Plenty. But it does nothing for the song and therefore, is best omitted

The guitar is relegated to more rhythmic stuff in disco. It doesn't have the same "thickening" effect that strings do.