yes you are right
there is an years of demand from nellore people to have an intercity(day time) express to secunderabad. so instead of running it in the same route(sc-Tpty) which are having more number trains try to run it to nellore or to vijayawada.
APSRTC Garuda buses which are running in between hyderabad-vijayawada is having an utmost demand and they are always fully reserved with in a few minutes. so instead of running it to guntur run in the wl-kmt-bza route