I actually think in this case it's ultimately okay because either "how or when" or "how or why" refers to the same thing: the fact that there's something fishy going on about who is double-crossing whom in the Stan/Nina situation. It is an important difference, though! The "when" conveys "at what point in the situation did he recruit Nina," while the "why" conveys "what made him want to recruit Nina."

Good catch!

-J