That might be true for a basic/early Rails app where it's ok to have script kiddie relationship with Ruby, but if you have a more complex app, I don't think the learning curve is quite as easy as you're making it sound.

My own experience with Rail is that I quickly wanted to see inside and control all of the implicit stuff that was going on, and I needed to invest a lot more time to learn Ruby to have the knowledge that would give the amount of control I wanted.