The "Default-Options=" keyword  is defined as the series  of options that
any NEW  subscriber acquires  when joining the  list (ADD  or SUBSCRIBE).
When you PUT a list, the subscribers you're sending along aren't normally
new subscribers, you're just replacing the  entire list. Most of the time
these subscribers were actually there  before. PUT (with subscribers) was
really designed to migrate  a list from site 1 to site 2,  not to add new
subscribers.
 
  Eric