When clicking on iPhone device, please make it possible to utilise ifuse, if it is available in system. It would be better comfortable than opening Terminal and mounting iPhone into an empty directory and then using umount as root to demount an iOS device. https://github.com/libimobiledevice/ifuse http://www.libimobiledevice.org/ If you need a tester, I am available.
Currently, Thunar mounts iPhone using libgphoto2, I guess. gphoto2://[usb:001,009]/
Gvfs handles this, Thunar has no idea what kinda of filesystem its accessing since its only communicated with GIO (which loads a GVFS backend to do the work).