Their comment wasn't based on using it but simply based on "Visual Studio on something other than Windows" more than likely.

Registration walls are only a bad idea when you care that a product reaches as far as possible. Given "Visual Studio on OSX/Linux" is going to drive humongous amounts of interest the extra metadata they get from the registration wall is worth annoying a few people.

On a side note several people have said that it is likely not available yet.