xrandr saying "Size 1920x1200 not found in available modes" even though it is available

Question

When I manually reduce resolution from 1920x1200 to some lower resolution in KDE (Debian 9 amd64), the command

xrandr -s 1920x1200

...does not work:

% xrandr -s 1920x1200
Size 1920x1200 not found in available modes

Well, the size 1920x1200 actually is available:

% xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 1200, maximum 32767 x 32767
HDMI-0 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    59.94    50.00    60.00    50.04  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      59.89  
   1280x1024     60.02  
   1280x960      60.00  
   1280x720      60.00    59.94    50.00  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       59.94  
   640x480       59.94    59.93  
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)

Setting output per answer https://superuser.com/a/1257312/200129 does not help:

• when I have resolution 1920x1200 set, executing command xrandr -s 1920x1200 flashes the screen.

• when I set lower resolution and add output monitor to command like xrandr --output HDMI-0 -s 1920x1200, nothing happens - not even screen flash.

P.S. command xrandr -s 0 sets mode 1920x1080, which is second mode from the top.