Heineman is more of a classic fifth OFer than Aquino. More versatile. Plays first, plays CF, corner OF obviously.
If it were a platoon situation, I might expect Reds to keep AA for PAs against lefties. But Reds won’t use a strict L/R platoon, they already have four regular type OFers needing playing time in three spots.
It also ties in with Strange-Gordon, he’s another lefty bat, if he makes the team then one of the RHH, Aquino or Heineman, could have a leg up as fifth OFer.