Yes that's exactly what I said.
Below is quoted from my protip above.
then we pass the same $@ to cd so that it uses the first argument passed to the function as well.
then the $@ tells mkdir to use the first argument passed to the function . In this case the dirName or the filetree that you input to the command mkdircd
Passing a second argument to this alias is not the point of this command.
Thanks for pointing that out though :P