[freehunter]

I'm not sure he's suggesting everyone should only ever use Chrome, but rather heading off "it doesn't work on my system!" complaints that are common with these tutorials. He goes into painstaking detail on exactly which version of Rails, exactly which version of Ruby, and exactly what gems you need to use to make sure the learner is using the same environment as the teacher. Suggesting that everyone use the same browser goes hand in hand with this. If you're a beginner and you run into compatibility issues with your browser, you might be turned off and quit. Making sure everything is the same while you're learning is really just good practice.