Sadhna's not speaking truth would definitely had released Ranveer out of jail, but would have sentenced another innocent person to jail (because Rakesh was lying in coma, so someone had definitely hit him). So, in place of Ranveer, another poor scapegoat would have to bear the punishment for hitting Rakesh. And this thought was shownto be conveyed during the rift track.
But now Anmol's truth cannot give anything other than taking away the support. Anmol's hiding truth will protect all the unprotected. BTW, I dont think there is anything to be hidden also from Anmol's side, he didn't kill Ranveer, it was an accident, only thing was Anmol would have died, if not Ranveer. Its like Sadhna's death for the child.
Its very much like comparing "why Sdahna could not speak lie topuching Bhagwad Gita" and telling Vinu that "she arranged the money from Mallika"...Actually, the morality behind Sadhna's "speaking truth touching Bhagwad Gita" could not be understood by many.