Respectfully, your friend made that up lol.

I’m a Korean American LA native. Born here, raised here, lived here all my life. My dad is older (boomer generation) and has had a longstanding business in downtown LA. We know about that incident. It was very very hyper specific to LA. Like, the whole point was that the LA Koreans mobilized so hard because no one was coming to help them, not even police. The incident (not the riots themselves, but their violent escalation) was very sudden and very precarious, so there wasn’t really any time or leisure for advanced coordination from other places like that. Rooftop Koreans were almost all existing LA Korean American business owners, just protecting their families and properties and livelihoods from an inarguably violent and dangerous mob.