WU generally follows the CCL, but doesn't use it exactly as there is no static CCL - X%. That being said, they seem to be using the following logic: reductions in the CCL dollar, update at 15:00 and 17:00 ART, appreciations, update once a day, increasingly after 17:00 when the markets close, and some times days later.
It used to be at 15:00 like clock work, but all last week I was waiting until after 17:00 to see an update, and often it was dozens of pesos below what the market closed at.