I worked with a guy who came through a bootcamp. Before he did it, he'd learned enough PHP to build basic sites, so he didn't come in cold. In the bootcamp, he learned Rails, and proper development habits like TDD and source control. He was a good junior developer when he started, and with two or three years of work at Pivotal Labs under his belt, he's a good journeyman developer. He taught me a lot of what i know about iOS development!
However, he mentioned that a lot of other people who came through the bootcamp with him have gone on to work at quite low-skill 'chop shop' web agencies, where they're mostly slinging HTML and CSS to match a photoshop drawing, rather than doing real programming as such. So, it doesn't work for everyone.
8 - 12 weeks spending 8 hours a day in a classroom is between 320 hours and 480 hours learning time, plus whatever additional effort the student puts in during evenings and weekends. It's plausible that a 12 week bootcamp could equate to 1000 hours of structured development time with a decent mentor. There are 3 year CS degrees that give a student far less.
But in general I agree with you that there's a big jump from enthusiastic newb to experienced veteran. It took me a couple years to figure out all the stuff that came after knowing how to code.