It’s absolutely possible they were all just terrible companies, but…
But publishing it here doesn’t make a difference, presumably the same information is on their CV.
Let me first say I think it's a terrible idea to publish this information publicly. The hiring company holds all the cards already, you don't need to give them additional power by showing yours. Companies understand this very well. But I get this has been done more for ideological reasons rather than practical ones.
Regarding the possibility that all companies were bad, that's actually important information that could point to the candidate's difficulty in evaluating opportunities. If that's an important part of the job which you're hiring for, you absolutely are going to take that into consideration.
I've been in the biz 13 years and only had 4 jobs but I felt varying degrees of "doing the job I wasn't hired to do" by two of them. This actually seems to have almost meme-status from others on the internet talking about their new jobs. Lots of these people stick around these jobs because, "Hey, I have a job!" but that's not for everyone. Some people, like the author of this post, have a bunch of cool personal shit under their belts (check the homepage) and afford to be picky.
The TL;DR here is that job interviews aren't always about an employer trying to impress a potential employee.