APG Accordion doesn't take nesting into account by advising against role=region

[accdc]

Within the Accordion design pattern guidance, the use of role=region is advised against when 6 or more regions are included, however this guidance does not take into account that there may be many such regions where the only way to ensure proper nesting information is to expose the relevant regions that are applicable.

Also, there are situations where the use of such regions is the only manner for identifying the boundaries between multiple expandable sections on the page, and not providing this information as a general policy causes more harm than the documented reason for not including it at all.

This came up because a client is choosing not to include the role at all as part of a general widget because they cannot anticipate how many such regions will be implemented by their own products, and here in the APG it says that there will be problems if they do, which is misleading and incorrect because it is more important to include accessibility features as a general practice than not.

[mcking65]

Related to #1002

[a11ydoer]

Discussed at ARIA APG meeting on 10/26/2021

[accdc]

Hi,
I have reviewed the guidance for Accordion in the 1.2 APG page, and it looks good to me now as is. The conditional statement "Role region is especially helpful to the perception of structure by screen reader users when panels contain heading elements or a nested accordion." sounds clear to me, and provides guidance for complicated scenarios without advising against the use of accessible features when needed.

[scottaohara]

Seems it might be a good idea to advocate for role=group for instances where one wants to avoid creating too many region landmarks, but also indicate boundaries for expanded disclosure widget content.