I did a little more testing. Both my iPAD and iPhone are running iOS 16.6.1. When I install the Microsoft RD App, it uses either "iPAD" or "iPHONE" as the clientname, regardless of what the name of the device is.
I have an older iPAD Mini running iOS 15.7.9. On this device the Microsoft RD App uses the iPAD's device name when the app is installed as the clientname. Note: If I change the iPAD device name after the RD app is installed, the clientname remains unchanged. If I uninstall the RD app and reinstall it, then the app uses the new device name.
This is a BIG problem, as I have multiple users with iPADs connecting to my server. Each iPAD needs to have a unique clientname, which does not seem to be possible if you are running the latest iOS release on newer Apple devices.