That's because until well into the development of Ruby 1.9, Ruby was still using the odd (dev)/even (release) approach. 1.9 introduced things that were differen

That's because until well into the development of Ruby 1.9, Ruby was still using the odd (dev)/even (release) approach. 1.9 introduced things that were different, and it wasn't stable enough for production use until 1.9.2, at which point work on 2.0 started.