I thought that was the classical influence, The Rite of Spring and Petrushka are like that too. Relayer may be the album where they got the closest to that music, they barely got there* with Wakeman in the band.
Perhaps. Though with Stravinsky's 'cut and paste' there's a melodic, harmonic or rhythmic logic that unites the disparate parts. They might seem episodic but it hangs together and I'm sure anyone with a score and an analytical brain could trace the links. I don't get that sense with Yes (understandably...they were working in a quite different environment) - seems more 'This sounds good, lets add this bit, how about this."
It always sounded natural to me. I remember seeing on the net - years ago- how someone had analysed Close to the Edge and decided it was in the same form as a sonata/concerto. I don't know enough about that sort of thing to know if it's true.