adb does not reboot my Samsung Galaxy SIII I9300 to bootloader (download) mode!

My device is Samsung Galaxy S3 I9300 and I did a complete factory reset. Device is NOT rooted yet. It works properly. I can do all of following with my device:

• Power off using device keys.


• Start in recovery mode and download mode using device keys.


• device is detected properly in normal mode and recovery mode by adb when is connected to PC through USB cable


• I am able to reboot device using adb reboot command


• adb reboot recovery works well.

The problem is that if I run adb reboot bootloader or adb reboot-bootloader commands, device is booted in normal mode, NOT in download mode. The only way to reboot the device in download mode is to use Power + Volume Down + Home keys