Nonsense. There are lots of things that you need more than three strikes for, especially on a platform that you expect to use for decades.
I'm not here to say that Facebook's enforcement behavior is optimal, and I don't know that a "17 strike policy" is a full description of their enforcement behavior. But there are plenty of behaviors that you want to discourage but not go nuclear about.
Seventeen is a "yeah sure it's not allowed wink wink" policy. Especially when they'll just go make another account afterwards.