No, he's being a bit stupid, security through obscurity is arguably no security at all however it makes identifying vulnerabilities _easier_.

The main issue for leaking source code of _games_, especially _multiplayer games_, is that people learn how to bypass the anti-cheat mechanisms which leads to a degraded online experience for everybody.

I worked on Tom Clancy's The Division and the mantra was always "write code like it will be public one day".

(in their case it meant don't get to persnickety about a library not working how you wanted or swearing about how Windows was batshit insane at times -- but it also applied to making sure you did't just assume the code wouldn't be read by malicious people)