Created attachment 88835 [details]
dmesg before suspend
this is happenning on a macbook pro retina 2013 (11,3)
when trying to manually shut down the display, or when the screensaver does it, the main display on the laptop only blanks the screen, but it doesn't shut down the backlight, if there are external monitors connected, it doesn't even blank the display.
after suspending and resuming the laptop, the command works, and also the screensaver shuts down the display properly
Created attachment 88836 [details]
X log before suspend
Created attachment 88837 [details]
Created attachment 88838 [details]
Xorg log after resume
It appears that your panel is connected via eDP. DP got a substantial rework in 3.16, among things fixed should have been the power management. Please see if the problem still exists.