I believe both trees had different types of hormones in their fruit. One particular tree would start puberty and sexual attraction in humans. Adam and Eve were as innocent children not knowing physical attraction. Choosing to eat of the forbidden fruit launched puberty and attraction, with God out of the picture.
God was waiting for them to ask the question on how to mate, since there was no physical drive to turn themselves on. They had no desire to become many and fill the earth so they did not ask him the question about sex drive. When the time was right he would have presented them to one of the trees for their next step.
Otherwise, if they were created fully mature Adam would have had intercourse with Eve the moment she was fully cooked and they would have had a perfect bun in the oven before the transgression. This would have created a paradox for God if the later was true. A number of perfect babies could have been born before the temptation. There would have been a world mixed with perfect humans and sinning humans.
The trees were meant to be hormone injectors. One tree launches procreation and one tree ensures errorless cellular reproduction.