18.04 – Why can not the left-handed touch panel be enabled through the xorg configuration?

I recently discovered that the libinput in Ubuntu 18.04 is defective, since it can only be configured temporarily through xinput, but not to xorg files: the following command can successfully set the LeftHanded property of my touchpad:

peng @ peng-tribbloid: ~ $ xinput set-prop 19 "libinput Left Handed Enabled" 1
peng @ peng-tribbloid: ~ $ xinput list-props 19
Device & # 39; ELAN1203: 00 04F3: 307A Touchpad & # 39 ;:
Device enabled (168): 1
Coordinate transformation matrix (170): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
Enabled tapping release (320): 1
libinput Tapping Enabled Default (321): 0
libinput Tapping Drag Enabled (322): 1
libinput Pressing Dragging Enabled Default (323): 1
libinput Tapping Drag Lock Enabled (324): 0
libinput Press Drag Block On Default (325): 0
Libinput touch button assignment enabled (326): 1, 0
Release of key assignment buttons Default (327): 1, 0
Natural displacement libinput enabled (302): 1
Natural display of libinput Enabled Default (303): 0
libinput Disable while writing enabled (328): 1
libinput Disable while writing enabled Default value (329): 1
Available libinput shift methods (304): 1, 1, 0
Enabled libinput scrolling method (305): 1, 0, 0
Scroll method libinput enabled Default value (306): 1, 0, 0
Speed ​​of acceleration of libinput (311): 0.205882
Accel Speed ​​libinput Default (312): 0.000000
libinput Left Handed Enabled (316): 1
libinput Left Handed Enabled Default (317): 0
Libinput Send Available Event Modes (287): 1, 1
Enabled libinput events sending mode (288): 0, 0
Libinput send event mode enabled Default (289): 0, 0
Device node (290): "/ dev / input / event28"
Device product ID (291): 1267, 12410
Libinput drag lock buttons (318): 6
Libinput horizontal scroll enabled (319): 1

But when I enable it in the xorg file (under /etc/X11/xorg.conf.d/30-touchpad.conf):

Section "InputClass"
Identifier "touchpad"
Driver "libinput"
MatchIsTouchpad "on"

# See http://manpages.ubuntu.com/manpages/bionic/man4/libinput.4.html for details
Option "TappingButtonMap" "lrm"
Option "ButtonMapping" "6 3 1 4 5 6 7"
Option "LeftHandedEnabled" "1"
Option "libinput Left Handed Enabled" "1"

Option "DragLockButtons" "6"
EndSection

After restarting, everything else in the file is configured correctly, except LeftHandedness:

peng @ peng-tribbloid: ~ $ xinput list-props 19
Device & # 39; ELAN1203: 00 04F3: 307A Touchpad & # 39 ;:
Device enabled (168): 1
Coordinate transformation matrix (170): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
Enabled tapping release (320): 1
libinput Tapping Enabled Default (321): 0
libinput Tapping Drag Enabled (322): 1
libinput Pressing Dragging Enabled Default (323): 1
libinput Tapping Drag Lock Enabled (324): 0
libinput Press Drag Block On Default (325): 0
Libinput touch button assignment enabled (326): 1, 0
Release of key assignment buttons Default (327): 1, 0
Natural displacement libinput enabled (302): 1
Natural display of libinput Enabled Default (303): 0
libinput Disable while writing enabled (328): 1
libinput Disable while writing enabled Default value (329): 1
Available libinput shift methods (304): 1, 1, 0
Enabled libinput scrolling method (305): 1, 0, 0
Scroll method libinput enabled Default value (306): 1, 0, 0
Speed ​​of acceleration of libinput (311): 0.205882
Accel Speed ​​libinput Default (312): 0.000000
libinput Left Handed Enabled (316): 0
libinput Left Handed Enabled Default (317): 0
Libinput Send Available Event Modes (287): 1, 1
Enabled libinput events sending mode (288): 0, 0
Libinput send event mode enabled Default (289): 0, 0
Device node (290): "/ dev / input / event28"
Device product ID (291): 1267, 12410
Libinput drag lock buttons (318): 6
Libinput horizontal scroll enabled (319): 1
peng @ peng-tribbloid: ~ $ 

Why is the left-handed configuration an exception? Is it an error in libinput?