Interesting. I went through a bootcamp recently. We started with sinatra (a slimmed down ruby application framework), then went into rails, and lastly used node+express.

If we had only done rails, I'd probably have little idea how it worked, but doing all three definitely shored up some weak points.

It also helped that the teachers were genuinely knowledgeable and we had short lectures on deeper-level stuff (we had one hour lecture on how to build a tcp server from scratch in ruby, one on how the internet actually works - from the link layer up, and so on).