The presumption is that seminary candidates aren’t or might not be emotionally mature. One question: are seminaries really the ideal place for developing such maturity? Granted, all of us have some growing up to do. A healthy and integrated person is always finding room for improvement, if not a deeper sense of sin and contrition. Sounds like something more suitable for a people in their thirties rather than teens.
317. We recognize the effort of those who are charted with formation in seminaries. Their witness and preparation are decisive for accompanying seminarians toward an emotional maturity that will make them suitable for embracing priestly celibacy and able to live in communion with their brothers in the priestly vocation; in this sense, the courses established for those in charge of formation are an effective means of aiding their mission. (In this regard the synod fathers exhort bishops to “assign the most suitable priests to this work, after preparing them with specific training for this delicate mission” EAm 40; Congregation for Catholic Education, Ratio fundamentalis institutionis sacerdotalis, 31-36; ID., Guidelines on the preparation of those in charge of formation in seminaries, n. 65-71; OT 5.)
For deeper examination, an English translation of the 2007 document from the Aparecida Conference.