A brief foray into Wikipedia reveals the following
https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes
It would seem that the return to land is only possible after SRBs are jettisoned.
Regarding the original question, I would be prepared to believe that 96.2% of the fuel load is required to carry the fuel load. It is just conceivable that that sort of statistic could be misrepresented by careless journalism as "96.2% just to get the the vehicle off the ground"!