Maybe the captain was a training captain and thus competent and licensed to teach the FO to land in such conditions...
And obviously how the FO would learn if he is not allowed to fly in some extreme conditions...
Rwy in Sight
Yes but one of THE fundemental rules of training/instruction in never getting into a situation with a trainee where if he/she mishandles it YOU do not have time to take over and recover with safety. The most important words in handling training are "I have control".