That's not a retention technique (even though it may work as such), that's a last ditch attempt.

A retention strategy makes sure that people never reach that page.

That's a retention technique in the same way that, "Don't break up with me! I Love You!" is a relationship reparation technique.

Not that I'd actually recommend doing it, but I'd bet that technique does work some small percentage of the time. What does Facebook have to lose by seeming desperate at that stage? I think it's smart.

Holy hell, that screams dating site unsubscribe system. I didn't realize Facebook was that low about account deactivations.