Even disregarding how much goodwill the company had burned at that point. Your solution implies that they would've set up a backup method once the employee left.
For most company the exit interview is done to tick a box. The feedback given will not be listened to at all. I can absolutely understand why he didn't feel like it was his job to setup and entire source control system on his way out the door.
For most company the exit interview is done to tick a box. The feedback given will not be listened to at all. I can absolutely understand why he didn't feel like it was his job to setup and entire source control system on his way out the door.