I don't use Heroku but, from the help page, it seems the point is to push users to learn the new syntax. I don't know if it's a good idea or not, but I can see

I don't use Heroku but, from the help page, it seems the point is to push users to learn the new syntax. I don't know if it's a good idea or not, but I can see how they got there. Without this, they'll never be able to remove the deprecated command.