afaict, work on grub2 started back in 2004, and a backport patch[1] of the 'paranoid' A20 checking for grub legacy was posted to the bug-grub mailing list back in 2006.
In fact, the very first reply[2] to that patch makes exactly the same point I did above: why not use grub2?
[1]: http://lists.gnu.org/archive/html/bug-grub/2006-07/msg00015....
[2]: http://lists.gnu.org/archive/html/bug-grub/2006-07/msg00025....