Comment by SiVal

Bigger tech companies not only do not host important private source code on Github but won't even host on outsourced physical servers. Where I've worked (incl. well-known names), information that we wanted spread to the world could be hosted on trusted external systems (trust still mattered to keep it from being "edited"), but non-public info was always hosted inside a physical building that we owned watched 24/7 by human guards we employed.