Hi!

As mentioned in the lecture this method only works against some routers, it won’t work against modern routers or ones that use PBC, Zaid still covered this though cause if it works then its a very good method to get the password as it is guaranteed.
See this method only works if the target uses pin authentication, because when PBC is enabled the router will refuse all requests and all pins even if we send it the right pin unless the wps button is pressed. If you are the attacker you won’t know if your target is using PBC authentication or not, you have to try this method, it is still works against some routers and if it is working it will give you a clear way to get a key.

Greetings!
Diego