grub + GPT BIOS boot partition

[Boylan, Ross]

The manual (3.4) says, for GPT and the BIOS boot partition
"With partitioning programs that require setting the GUID directly, it should 
be ‘21686148-6449-6e6f-744e656564454649’.

Caution: Be very careful which partition you select! When GRUB finds a BIOS 
Boot Partition during installation, it will automatically overwrite part of it. 
"

Does this mean that the installer will overwrite the BIOS Boot partition on 
every disk that has one (since they all have the same GUID), or only on the 
target disk?  Giving the same GUID to different partitions seems like a recipe 
for trouble.  Or is the GUID some type flag in GPT and not the partition UUID?

What happens with a GPT disk that does not have a BIOS boot partition?

I'm also a little confused about the role of the BIOS boot partition vs /boot 
for Linux systems.  I thought the installer wrote itself into /boot.  Is it 
that some of the key components also go in BIOS boot so that grub knows enough 
to be able to read /boot?

Thanks.
Ross Boylan

cc's appreciated.