Le Yu had also realized that there were way too many holes in this "Hidden Yin" identity.
A lone white-haired assassin infiltrating upper-class society to gather intel just didn't make sense—Hidden Yin's choice to stay hidden in the slums, coordinating and relaying info, actually made a ton of sense. Thanks to his hair color, the odds of him getting exposed were sky-high, plus nobody would ever trust an assassin with terminal white hair anyway.
White Night's setup was definitely smart: assigning Hidden Yin to handle logistics, assassinations, and backup—the stuff he was actually good at. And he pulled it off like a pro.