You are mistaken, sorry. Even the normal everyday infotainment on most modern cars has receive-only telemetry available to it from the car control computers. Some elements are passed through (like EV state of charge) to old style CarPlay as well. Think data diode (making no claims as to the actual physical implementation, but logically it works)

CarPlay Ultra is just an extension of that where the gauge cluster is now just another infotainment screen that displays the received telemetry data. It does not have access to the ECU, cannot interfere, can be rebooted with impunity, etc.