No, incorrect. This is a modification to your .bashrc, which is (already) run every time you start a bash process, within that process (i.e., not a new process). Nothing needs to be spawned on every single process.
Admittedly the bash script does spawn some processes, but a) that's the way .bashrc works, and you have dozens of those in there, and b) it's only one process, a mkdir. The echo and the conditional run within bash itself.
The way that the configuration works, whether done in the kernel or in your .bashrc, is to associate all processes spawned from a single bash shell with a single new scheduling group. This gets you better performance when you're running processes from terminals, by associating logically-similar groups of processes in the kernel instead of letting it see all the processes as a giant pile.
The intended use case, which is pretty clear from the LKML discussion, is to make performance between something intensive (like a compilation) in a terminal and something non-terminal-associated (like watching a movie) better-balanced.