I have a similar background, and my initial path into this job in the late 90s was definitely "become a developer in 6 months" using only books on HTML and Perl (and a pirate copy of Photoshop), so I can easily believe with instruction one can become a developer in 3.
There's a lot I couldn't do, of course, and there will be a lot that bootcamp devs can't do. But it's a start, a foot in the door. And it's also a kick up the ass for anyone who doesn't have the discipline to just sit at home studying for months.
I suspect both you and I made useful contributions before we hit the 10 year mark, if your young devs are just doing menial work either they're just not very good or they aren't being given anything solid to work on.