What part of "so let’s just consider it an expensive learning opportunity to redesign the system so it can’t happen again" doesn't mean that it's happened, but let's see how we get there.
"It should not have been possible for one person to take the site down" - yes, and that's exactly what Zuck is addressing here? May be such controls are there across the development teams and some SRE did something to bring it down and now there needs to be even better controls in that department as well?
As told this is clearly not a Zuck quote because it’s shitty leadership. There’s no way Facebook got where it is with such incompetence. This is clearly a mistelling of older more coherent anecdotes.
It should not have been possible for one person to take the site down. There should have been controls in place to prevent it.
There shouldn’t even be someone that “everyone knows” is responsible, because by definition that’s impossible.