the joke being assist is more of a football(soccer)/basketball/ice hockey term than it is a volleyball term
if you're a setter the best thing you can do is get a one-on-one or an empty net, beyond that, it's the attacker
He was inspired by Japan's women's basketball team because they won gold during Tokyo. It was discussed here before VNL but I don't recall the exact details. I think it has to do with becoming more synchronized / better flow and control.