I don't think it's all that unreasonable, actually. I use Ubuntu and Unity has caught my eye. I would definitely try it if it had a Linux editor, but I'm not going to install Windows just to try it out.
I think it's about the comparison to PHP/HTML which might be usable in other areas but definitely not for 3d games/applications. It might be different with JS and WebGL but PHP is for a completely different use case than Unity.
