I too am confused as to why the author has chosen to include their entire Bash configuration in this repository. As far as I can tell, this is the only interesting file:
I also wasted a fair amount of time looking through these files, trying to figure out what all the miscellaneous bash configs had to do with the stated purpose. I did find that there is a nice undocumented feature of the cdff command, which allows you to specify the directory of a window lower in the stack by sending a numeral as the positional parameter.
On a similar note, if you just want to open a new Finder window to the current working directory (instead of using an existing Finder window), just use
open .
The 'open' command has tons of uses (open a file with a specific application, reveal a file in Finder, open a URL in the user's browser, etc.) and I recommend reading its man page.