[chef] precedence is different, so why are values merged

[bradford < >]

ntp has the following in attributes/default.rb:

    default['ntp']['servers']  = %w{ 0.pool.ntp.org 1.pool.ntp.org
2.pool.ntp.org 3.pool.ntp.org }

i added the following to my development.rb:

    default_attributes( "ntp" => { "servers" =>
["0.north-america.pool.ntp.org", "1.north-america.pool.ntp.org"] })

but i see all 6 of them in ntp.conf.  on irc someone said that when
the precedence is the same, they get merged; but, according to the
docs [1] the precedence is not the same:

The precedence of the attributes - from low to high

    default attributes applied in an attributes file
    default attributes applied in an environment
    default attributes applied in a role
    default attributes applied on a node directly in a recipe
    normal or set attributes applied in an attributes file
    normal or set attributes applied on a node directly in a recipe
    override attributes applied in an attributes file
    override attributes applied in a role
    override attributes applied in an environment
    override attributes applied on a node directly in a recipe

[1] http://wiki.opscode.com/display/chef/Setting+Attributes+%28Examples%29