Tested with macOS Ventura and xcode 14.
Files can be added by:
This is the easy way but image/video files are always added to the Photos app. Other kind of files like PDF are added to the Files app.
Example: xcrun simctl addmedia booted pic.001.jpg
This has the same behaviour as option 1
but can be automated.
username/Library/Developer/CoreSimulator/Devices/*device_hash_folder*/data/Containers/Shared/AppGroup/*hash_folder*/File Provider Storage/
This allows copying any kind of file so it's available in the Files app (locally on my iPhone folder).
The following script opens the File Provider Storage of the currently booted simulator:
SIM_UDID=$(xcrun simctl list devices | grep Booted | perl -n -e'/^.*([0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}).*$/ && print $1')
FILES_PATH=$(xcrun simctl listapps $SIM_UDID | grep LocalStorage | awk -F'"' '{print $4}' | sed -e "s/^file:\/\///")
open $FILES_PATH/File\ Provider\ Storage