The file /usr/local/etc/grub.d/10_kfreebsd is generated from a script that has '\t' characters that expand to 't' characters instead of TAB characters. This means the resulting /boot/grub/grub.cfg file doesn't work as expected... How-To-Repeat: Install sysutils/grub2 and have the system install a grub.cfg file. Look at the result...
*** This bug has been marked as a duplicate of bug 187165 ***