> Having an entirely different developer browsers makes the debugging experience less realistic. It puts you in a position where you don't truly experience what the user does but what you feel more comfortable experiencing.

I don't really agree with this part; it's going to be using the same rendering and JavaScript engine so I wouldn't expect the experience to be different at all it'll just have far better access to developer tools.

Having said that, Mozilla didn't exactly put much of any content into their blog post so I could end up being wrong.