That's a pretty impressive way to hand-wire a keyboard. Being a 9-key keyboard, you can wire each switch to it's own pin and remove the need for diodes and still have independant keys (N-key rollover). Expanding this to a larger keyboard would require making room to fit some diodes in there as well. And while hand-wired keyboards make a fun project, building a custom PCB isn't too difficult or very expensive either. Incorporating something like this into a Dactyl type ergonomic keyboard where PCBs are more difficult to use could be interesting though.