Earlier quoted context omitted.
Newly introduced errors in site code are only one of many sources of failure for a site like GitHub, and probably a fairly rare one.
It's a nearly weekly occurrence. Avoidable one, I might add. When was the last time a major Google service had a major outage?
When I said "probably a fairly rare one", I didn't mean that the outages are rare. I meant that new code is probably a rare cause of the outages that happen. They have other causes unrelated to new code.
(I'm also skeptical that GitHub major outages happen "nearly weekly", but I don't have data.)