jmtpfs device confusion

# JMTPFS mounts -- yes, the directory /media/android is owned by me
# I am redacting the VID, PID and model name, but on my system, it does show up.
user@stretch:/media$ jmtpfs /media/android
Device 0 (VID=xxxx and PID=yyyy) is a ******* ***** (MTP).
Android device detected, assigning default bug flags

# extsdcard is my removable storage (external sdcard)
#"Internal shared device" is the system storage
user@stretch:/media$ ls /media/android
extsdcard  Internal shared storage
# Contents of my removable storage device
user@stretch:/media$ ls /media/android/extsdcard
Android  contacts.vcf  documents  go-mtpfs  lost+found  music  new  something-else  something-new  yes.txt
# As a test, I touch a file on the removable storage device
user@stretch:/media$ touch /media/android/extsdcard/forums-test
# ...and in Debian, I can see the file exactly where I'd expect it to be.
user@stretch:/media$ ls /media/android/extsdcard
Android  contacts.vcf  documents  forums-test  go-mtpfs  lost+found  music  new  something-else  something-new  yes.txt

# Now let's enter Android shell to check
user@stretch:/media$ adb shell
android:/ $ su # I enter root to access all possible devices
android:/ # busybox find / -name forums-test
/storage/emulated/0/forums-test
#   ^emulated/0 right here is my internal system storage, not my removable device
/mnt/runtime/write/emulated/0/forums-test
#   ...and again
/mnt/runtime/read/emulated/0/forums-test # and again
/mnt/runtime/default/emulated/0/forums-test # and again
/data/media/0/forums-test
#   ^ This is the "real" mountpoint of the internal storage, and again, not the removable partition

# Strange, right?  Now let's see what happens when I "ls" my removable storage's mountpoints...
android:/ # ls /storage/67* # FUSED external sdcard directory
Android       documents  lost+found  something-else  sure
contacts.vcf  go-mtpfs   music       something-new   yes.txt
android:/ # ls /mnt/media_rw/* # Actual external sdcard directory
Android       documents  lost+found  something-else  sure
contacts.vcf  go-mtpfs   music       something-new   yes.txt
# Nothing, and nothing again.

#  How disappointing. Lastly, from within Android, I try the reverse: touch a file, and try to view it on Debian
1|android:/ $ cd /storage/67*
android:/storage/674c7168-e937-4d84-988c-3c8078219ff2 $ ls
Android  contacts.vcf  documents  go-mtpfs  lost+found  music  something-else  something-new  sure  yes.txt
android:/storage/674c7168-e937-4d84-988c-3c8078219ff2 $ touch forums-test2
android:/storage/674c7168-e937-4d84-988c-3c8078219ff2 $ ls
Android  contacts.vcf  documents  forums-test2  go-mtpfs  lost+found  music  something-else  something-new  sure  yes.txt
# forums-test2 was successful.  Now, to check it in Debian.
android:/storage/674c7168-e937-4d84-988c-3c8078219ff2 $ exit
user@stretch:/media$ ls android/extsdcard
Android  contacts.vcf  documents  forums-test  go-mtpfs  lost+found  music  new  something-else  something-new  yes.txt
# Nothin'
user@stretch:/media$