It's irrelevant because 1) you can't always trust someone saying "friendly, friendly" or claiming to be offering medical assistance while brandishing an AR-15 at the ready position and 2) the "friendly" claims happened after Ritten was already following them and accelerated himself straight into this group that you claim is trying to "coordinate an ambush. The only time the video appears to show him shouting medical was before it looks like he even reached the Rosemblaum group so its entirely possible they didn't even hear that claim from Rittenhouse.
Even granting your characterization of the victim and other protesters, it just shows how reckless Rittenhouse was behaving that night charging right into a situation that he either A) completely lacked the situational awareness to understand how reckless he was behaving or B) didn't care. As the photo that Dwazza posted, Rittenhouse's appearance brandishing the AR-15 itself appears extremely threatening and provoking. That person following and then accelerating in pursuit would, to me, be an extremely threatening action and in this case it was clearly reckless behavior.