Seeking clarity regarding the terminology in Success Criterion 1.2.5 Audio Description

Warning, it is a bit challenging to describe my concern so this is a bit 
verbose.

Success Criterion 1.2.5 Audio Description (Prerecorded) states, "Audio 
description is provided for all prerecorded video content in 
synchronized media."

In the normative part of the SC there are no exceptions, thus my 
interpretation is that an Audio Description is always required for 
synchronized media. Where it gets tricky for me is the definition of 
Audio Description.

When reading the Understanding (non-normative) doc for 1.2.5 the term 
Audio Description appears to me to be ambiguously defined. I would argue 
that the term is being used in some parts of the document to mean a 
separate audio track that augments the integrated (main) audio of the 
synchronized media to describe visual details, but in other parts to 
mean a description of visual details that may be in the integrated audio 
OR a separate audio track.

So which is is it? Is Audio Description defined describing in audio the 
visual content as separate track? Or, is Audio Description defined as 
describing in audio the visual content within the integrated (main) 
audio OR as a separate track.

This is important, because if WCAG defines Audio Description as always 
being a separate track, then the SC (normative) requires a separate 
track for all synchronized media.

Some examples of ambiguous language:

/In the Understanding doc (Note section below "Intent") the following is 
stated, "For 1.2.3, 1.2.5, and 1.2.7, if all of the information in the 
video track is already provided in the audio track, no audio description 
is necessary."/

My interpretation of that language is that audio description is a 
separate track, but is only necessary if the main audio track does not 
sufficiently describe the visual content. The problem is that this 
directly conflicts with the SC, "Audio description is provided for ALL..."

/In the Key Terms section audio description is defined as "//narration 
added to the soundtrack to describe important visual details that cannot 
be understood from the main soundtrack alone".
/

Again, this implies that there is a 2nd (separate) soundtrack.

My sense is that the term Audio Description is being used to have two 
different meanings (ambiguous). In the SC statement it means that the 
visual content must be described (either in the integrated audio or a 
separate audio track) and in the Understanding doc it means explicitly a 
separate audio track.

Thoughts?

Greg