It is stupid but 2 of those players were put on at '119. Normally I wouldn't think that but in this case the England team and supporters were pushing the diversity thing hard. But you said it yourself. Why put the inexperienced teen at the 5 spot? Had England won, diversity would have 'won', if they lost, well, now they can spin their loss.
Like I said, I normally wouldn't assume this but putting all 3 right at the end? I don't doubt Southgate had an agenda. Hell, he may get a knighthood, for LOSING lol.