[DNA] MUST NOT add DNA Option when landmark RA = NO?(draft-pentland-dna-protocol-00.txt)

[Greg Daley <greg.daley@eng.monash.edu.au>]

I'm confused by this statement in the draft:

In Section 5.1.4:

"... If the RS contains a Landmark Option whose prefix does not
  match any of those in the interface's stored prefix list, then
  the Landmark option with the Landmark prefix is included in the
  RA but with the No flag set.  All fixed options (MTU,
  Advertisement Interval, flags, etc.) are added to the Router
  Advertisement.  Prefix Information Options for any explicitly
  configured prefixes SHOULD be added to the Router
  Advertisement, while the DNAO for learned prefixes MUST not be
  added."

Is there a reason why DNAO MUST NOT be sent in this case?

Isn't it useful to indicate immediately which of the
prefixes are available on the new link?

Greg