I have done the 5.5 and the 12.9 but I can't enrol the device for Touch ID in hardware for either of the 6.5 inch devices in the simulator.
Taking a screenshot of the device in action in the simulator seems much more simple and is the way I've found works best.
Is it possible? Seems strange if it's not.
I've managed to resize a 5.5 inch screenshot to 6.5 inch (1242 x 2688) on this site- https://onlinejpgtools.com/resize-jpg.
It has loaded to App Connect seemingly without any issues. I'm keeping my fingers crossed though🤞🏻