I don't know if anyone else has seen this cutscene before, but I haven't. I discovered it while attempting this stage for Yuan Shao's Musou Mode. If I had to guess how it triggers, it's when you leave Zhang He isolated for a set period of time, then go meet up with him after the "It cannot end here" dialogue. Just when you think you know everything about this game, something else pops up to surprise you.
