That is correct. However, the camera may overheat if you stream at 4K for several hours. The Wi-Fi chipset generates additional heat.
It may work, but it may overheat. If you use the plug-in, then test it prior to the auction, possibly in a room with limited airflow so you can prepare for a worst-case scenario.
The wireless live streaming plug-in will likely work for a long time at 2K.
If you already have a Z1, you can download the plug-in and test it overnight. The plug-in is free.