It's because them emphasizing how the do-not-track setting should reflect a deliberate decision by the user.
The current draft of the document concerning DNT is also written in this way:
I guess NoScript might be OK because of:http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html#determining wrote:The goal of this protocol is to allow a user to express their personal preference regarding tracking to each server and web application that they communicate with via HTTP […]
Key to that notion of expression is that it must reflect the user's preference, not the choice of some vendor, institution, or network-imposed mechanism outside the user's control. The basic principle is that a tracking preference expression is only transmitted when it reflects a deliberate choice by the user. In the absence of user choice, there is no tracking preference expressed.
(emphasis by me)For example, a user might select a check-box in their user agent's configuration, install an extension or add-on that is specifically designed to add a tracking preference expression, or make a choice for privacy that then implicitly includes a tracking preference (e.g., "Privacy settings: high").