Level AA exceptions

As more and more policies and regulations adopt both level A and AA and 
thereby place more of the responsibility and burden on the web content, 
the notion of the difference between and rationale for having Level A and 
AA is getting lost and misunderstood. 

Is there still general consensus that there are interacting issue that 
need to be considered when applying Level AA Success Criteria to all web 
content and web applications? 

See Understanding Levels of Conformance 
http://www.w3.org/TR/UNDERSTANDING-WCAG20/complete.html#uc-levels-head
"The Success Criteria were assigned to one of the three levels of 
conformance by the working group after taking into consideration a wide 
range of interacting issues. Some of the common factors evaluated when 
setting the level included:
whether the Success Criterion is essential (in other words, if the Success 
Criterion isn't met, then even assistive technology can't make content 
accessible)
whether it is possible to satisfy the Success Criterion for all Web sites 
and types of content that the Success Criteria would apply to (e.g., 
different topics, types of content, types of Web technology)
whether the Success Criterion requires skills that could reasonably be 
achieved by the content creators (that is, the knowledge and skill to meet 
the Success Criteria could be acquired in a week's training or less)
whether the Success Criterion would impose limits on the "look & feel" 
and/or function of the Web page. (limits on function, presentation, 
freedom of expression, design or aesthetic that the Success Criteria might 
place on authors)
whether there are no workarounds if the Success Criterion is not met."

So, that says to me that Level AA Success Criteria are not "essential", 
some may not always apply to all types of content (e.g. contrast on 
complex visualizations), some may require skills that cannot always be 
reasonably achieved by the content creators (e.g. video descriptions), and 
that it may impose limits on the "look & feel" and/or function (e.g. more 
images / less text), although I believe those success criteria imposing 
limits were identified as Level AAA. 

In other words "...you are advocating that AA success criteria should have 
more 'wiggle room' than Level A Success Criteria" ? 
Yes, because the working group reached consensus on making it level AA 
instead of Level A because of the wide range of interacting issues. 
However, none of the supporting documents (Note1) have listed the specific 
"interacting issues" per individual success criteria for why it was 
assigned level AA or level AAA instead of level A.  Yes there are 
exceptions listed where appropriate for both Level A and AA Success 
Criteria, but those are not the all the issues discussed that caused the 
criteria to be assigned as AA instead of A.  Most if not all the 
"interacting issues" are logged deep in the e-mail archives of the working 
group. 

So, should there be documentation added on the rationale for why a success 
criteria was assigned level AA (instead of A or AAA) to help practitioners 
better understand "how to apply level AA success criteria" as compared to 
applying Level A success criteria?   For example, should a non-normative 
section be added titled  "Rationale for assigning this SC to Level AA" be 
added  to the Understanding WCAG 2.0 guide? 

Note 1: Supporting documents:
1. Understanding WCAG 2.0 
http://www.w3.org/TR/UNDERSTANDING-WCAG20/complete.html
2. How to Meet WCAG 2.0 http://www.w3.org/WAI/WCAG20/quickref/
 
____________________________________________
Regards,
Phill Jenkins,