Wait what? I don't get why performance improvement implies reliability and incident improvement.

For example, doing dangerous thing might be faster (no bound checks, weaker consistency guarantee, etc), but it clearly tend to be a reliability regression.

First, if a performance optimization is a reliability regression, it was done wrong. A bounds check is removed because something somewhere else is supposed to already guaratee it won't be violated, not just in a vacuum. If the guarantee stands, removing the extra check makes your program faster and there is no reliability regression whatsoever.

And how does performance improve reliability? Well, a more performant service is harder to overwhelm with a flood of requests.

Less OOMs, less timeouts, less noisy neighbors problems affecting other apps