Ruby's also got a much better web dev story, which is good for junior devs (without ML and/or infrastructure backgrounds) who are looking to enter the market. After learning Ruby, either JS or Java could be a great 2nd language.
> It's much more beginner friendly and is a thoroughly consistent OO language—i.e., everything is an object, including numbers and strings.
This sort of thing occurs to you and me and makes sense because we have a broader understanding of software engineering. In practice, I just don't think "everything is an object" means much to someone who's a month into a bootcamp.
IMO learning very beginner-friendly language like Ruby to a low-intermediate level first actually speeds up the process of getting to an employable level with a more difficult language like JS.
Also, most languages have quirks. What are you going to teach them? Python, which also has almost 30 years of baggage? Java, which requires you to spend significantly more time to produce basic functionality? Haskell, so they can gloat about the power of purity and monads on Hacker News?
I understand that javascript might not be the ideal intro language in theory. But I think it probably is the best one in the bootcamp specific use case.