Platform 1 & 2 are terminals for trains coming from Delhi or Moradabad side. So they are useless for non-terminating trains at Saharanpur.
Platform 3 & 4 are made sequentially. So one of then becomes useless if a full length trains covers the other. Thus for trains coming from Delhi or Moradabad and going ahead , there are actually only 3 useful platforms out of 6. That seems irony.