"Live CGI" in particular expresses something very important about the tech - that it can be used in combination with other on-set tools and props, and cuts out

"Live CGI" in particular expresses something very important about the tech - that it can be used in combination with other on-set tools and props, and cuts out much of the "parallel workflow" that is currently required to composite a CGI scene. You don't get the same concept out of "real-time" or "instant" because game engines are "real-time CGI," and "instant" has an existing association with "pre-packaged" - e.g. "instant coffee." "Automatic CGI" might also work. It's not 100% accurate but it would provoke people to say "what's so automatic about it?" And from there you can explain how now the camera operator can move around a CGI set freely, etc.