It would have not made any difference whether Bhutto accepted it or not because he had no authority.
West Pakis gave votes to PPP and East Pakis gave votes to AL of Mujib. There your so called UNITY went down the drain.
Being highest winning seats of combined Pakistan, it was Yahya Khan who had to offer to Mujib for formation of government. But Yahya though under whom the elections were very impartial and transparent, took a very stupid action by banning AL and started military action.
GET YOUR FACTS CORRECTED.