As you know, in families the youngest child often gets away with far more than the eldest child was ever permitted. I suspect that this part of Benedict’s Rule was to combat this tendency. In a religious order as soon as the juniors have some relaxation in the Rule, the rest soon want to follow. There might also be a hidden reference here to Proverbs 22: 6, ‘Train up a child in the way he should go, and even when he is old he will not depart from it’. If you insist on the juniors doing this properly, then they will still be doing things properly all through life. This part of the Rule might also have been there to stress to the abbot just how important keeping discipline in this area is – he might choose to mitigate the whipping a bit, but at least with the Rule’s encouragement he will always do something to reinforce to the youngsters that their behaviour is unacceptable.
The ‘both / and’ description is one that is often used on The Journey Home programme on EWTN. It seems to hold true for quite a bit of the Catholic faith. eg. Scripture and tradition rather than ‘sola scriptura’; prayer and penance; unity and diversity.