I'm pretty skeptical about that kind of school too.
I graduated from an French engineering school and I was taught every-day by researchers and professional engineers. That's what most 18 to 23 year-old kid needs. Structure. I know I needed it. I was a dumb 20 something year old.
Plus, that kind of school focuses too much on programming, as in using programming language, and not enough on computer science and engineering. As a result, much of the kids arriving on the job market don't really have an engineering approach to building software. I've seen people using one programming language for most of their carreer, litteraly afraid of switching to another one.
Some may feel that the job market is saturated by programmers looking for a job but the truth is, in France anyway, not much have a good engineering mind. I've worked in big companies, i've worked in small companies and I've talked to a lot a recruiters. They do interview a lot of people, from university, engineering school and other formation structures. Truth is i've seen big and small companies recruting students that had majored in anything but CS, juste because they came from an engineering school or university that was known to produce good engineers.
Most of those students reavealed themselves to be very talented software engineers. Because they were taught engineering. Not just programming.
Of course, students that had majored in CS from engineering had a great head start, but my point is, the engineer skill is really important on the programmer job and most of those bootcamp school overlook it.