How did Paul have as much time with Jesus as the twelve?
Paul's three years were not spent traveling Palestine with Jesus as the twelve did, but in Arabia and at Mount Sinai under private tutelage from the Lord Himself. That period gave him equal standing with the twelve, so he was not one whit behind them in time spent with the Lord.
Les explains that Paul’s critics argued Peter and the others had three years with Jesus, going up and down the dusty roads of Palestine, while Paul did not. Les says Paul may not have spent three years in Palestine, but he spent three years in private tutorage from the Lord Jesus Himself. That is why Les thinks the three years at Mount Sinai/Arabia were necessary: not just to learn what Paul would preach, but to give him the full authority of time spent with the Lord, so he was not one whit behind the twelve.