Bug#502446: debian-installer: grub-installer is not updated for grub-pc introduction
As I looked more in detail, debian-installer works fine (does not over
write unrelated data) and usable if MBR is used as BIOS emultion mode
boot loader. (I.e., installed to /dev/sda (hd0)
So problem is when installing to /dev/sda3 or in other word to (hd0,3).
Since this causes data loss, this could be considered grave. But
changing d-i this late may not be good idea. If so reminder not to
install to places such as /dev/sda3.
Anyway, installation needs to do few manual tricks including gptsync.
Documenting this as short comments in release note is good idea.