So instead of not remembering "tar xfz", you can not remember "mac tar:extract"? Either way, I guess you'll just end up asking google and google will tell you to use tar.
man <command>.
And if people are in the command line often enough, they do memorize the actual commands. They really, really do.
man pages don't really solve the discoverability problem.
Isn't this just layering the discoverability issue? It's another set of commands to learn, when you should be learning the real commands.
Isn't that what apropos is for?
Exactly. In addition to that, this is a chance to collaborate to build more and better commands. It's the first step to what could be a powerful and very useful developer tool.
There's already been collaboration among the various *nix operating systems.