That kind of OJT will kill you when you make a mistake. In training you get a second chance.
Nobody is sending anyone anywhere "untrained." Not implying that you said that, but the author gives the impression that they're taking recruits, dressing them up, and sending them on patrol in Sadr city the following week with a Petraeus handbook.
The point is, once trained on the basics, which gives a better environment to learn "tough, realistic" training--an Army base, or a real war?
A pilot always has to solo for the first time, eventually.
A high-rise construction worker has to step out on the 34th floor eventually.
Which pilot do you want to fly with? Which construction worker do you want walking near you on a beam?
The one that's been through "tough, realistic" training for a year....or one that's been in the real world for 3 months?