I'm not the biggest job-hopper, but I've worked at 3 companies in the last 5 years in the NYC area, and have never once worked with, known anyone who's once worked with, or knew a hiring manager who would even consider someone whose only significant background in software was a coding bootcamp. For those who've experienced it, are they hired out of desperation into firms that need manpower and have enough more senior…
Of course, anyone coming out of a bootcamp (or undergrad if they have no work experience) is going to be a relatively inexperienced hire, and not all companies have the inclination/ability/experience/desire to support these kinds of hires and the mentorship they require.
I've been a hiring manager for a very long time, and my opinion is that it's foolish to dismiss any potential source of candidates, especially one where you are not directly competing with google/facebook/amazon/goldman sachs. Many people from flatiron have engineering or math degrees, and realized after school they loved to code.
Also, back in the day, when I was a sophmore in college, someone hired me to be a sysadmin when the only experience I had was running the network in my college dorm for 6 months. Within a very short time I was writing all kinds of code, learning a ton, and making small but meaningful contributions. I've worked as a software engineer ever since. My first boss took a risk on me, and it worked out really well for him, and me. Some of the best hires I've ever made had skillsets that didn't, on paper, line up very well, but they turned out great. These experiences are why I'm willing to take risks in hiring.
I think most hiring managers are far too narrow minded when it comes to this stuff, although I understand why that's the case, too.