I doubt Manning, Clausen or Ainge would have been recruited if a strong bench press were required.
Kevin Durant couldn't bench press 185 once during his NBA draft combine. That didn't affect him one bit in becoming one of the transcendent athletes of his generation. Bench Press literally has next to no correlation with a QB's success. If you are drafting QBs based upon their bench press performance at the combine, then you end up with Jim Druckenmiller.