Question: Do highly academic schools like Stanford and the Ivy Leagues recruit later due to the need for grade transparency?
Answer: To some degree you have answered your own questions. The highly selective academic schools such as the Ivy Leagues and the baby Ivy Leagues usually can't make commitments or request commitments before the end of the player's junior year because they cannot guarantee her admission.
Most of the time, the earliest they can get approval for possible admission for the player is at the end of her junior year. That means they are less likely to request commitments before that time. Most admission offices want to see both test scores and 6th semester transcripts before giving a student serious consideration.