Linux boot loader and boot flag sensitivity

Noting down the observation:

Grub boot loader is not sensitive to boot flag setting of the boot partition. If the boot flag is not set for the boot partition or has been wrongly set to non boot partition it can boot the Linux.
On the other hand extlinux boot loader is sensitive to boot flag settings. If boot flag is not set for the boot partition, it fails to boot the Linux machine with error “No boot device found”.