Grub2 documentation of the GRUB_CMDLINE_*XEN* parameters -- unclear. What's _intended_?

[PGNet Dev <pgnet.dev@gmail.com>]

Grub2 documentation @ 
https://www.gnu.org/software/grub/manual/grub.html#Configuration states

	...
	‘GRUB_CMDLINE_XEN’
	‘GRUB_CMDLINE_XEN_DEFAULT’

	    The values of these options are appended to the values of 
‘GRUB_CMDLINE_LINUX’ and ‘GRUB_CMDLINE_LINUX_DEFAULT’ for Linux and Xen 
menu entries.
	‘GRUB_CMDLINE_LINUX_XEN_REPLACE’
	‘GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT’

	    The values of these options replace the values of 
‘GRUB_CMDLINE_LINUX’ and ‘GRUB_CMDLINE_LINUX_DEFAULT’ for Linux and Xen 
menu entries.
	...

 From these docs. it's not clear which values get mapped to which grub 
entries.  One set 'appends', one set 'replaces'.  Are they exclusive of 
one another?

And, what specifically gets mapped to Xen kernel's "options=" parameter 
line?

E.g., a grub2-mkconfig-generated xen*.cfg takes the form

	# disclaimer
	[global]
	#default=

	[config.1]
	options= dom0_mem= ...
	kernel=vmlinuz-4.3.0-16.gff1dcd9-xen ...
	ramdisk=initrd-4.3.0-16.gff1dcd9-xen ...

whereas for a NON-xen grub*.cfg

	# disclaimer
	[global]
	#default=

	[config.1]
	kernel=vmlinuz-4.3.0-16.gff1dcd9-default ...
	ramdisk=initrd-4.3.0-16.gff1dcd9-default ...

there's NO "options=..." line.

The docs should clearly address which PARAMETERS map to the "options=" 
line, and which to the kernel=" line in the Xen case.

To get there -- What's intended, by designn, from development in these 
specific *XEN* cases?