Clarification for exposure of generic elements (#1949)

closes w3c/html-aam#489
closes #1829

reworded the last paragraph of the generic definition to indicate that it can be ignored when not providing information important to the a11y tree, but if it does provide such information, then the generic element should be exposed.

Author: scottaohara

index.html

@@ -3637,7 +3637,8 @@ <h2>Definition of Roles</h2>
 			<div class="role-description">
 				<p>A nameless container <a>element</a> that has no semantic meaning on its own.</p>
 				<p>The <code>generic</code> role is intended for use as the implicit role of generic elements in host languages (such as HTML <code>div</code> or <code>span</code>), so is primarily for implementors of user agents. Authors SHOULD NOT use this role in content. Authors MAY use <rref>presentation</rref> or <rref>none</rref> to remove implicit accessibility semantics, or a semantic container role such as <rref>group</rref> to semantically group descendants in a named container.</p>
-				<p>Like an element with role <rref>presentation</rref>, an element with role <code>generic</code> can provide a limited number of accessible states and properties for its descendants, such as <pref>aria-live</pref> attributes. However, unlike elements with role <rref>presentation</rref>, <code>generic</code> elements are exposed in <a>accessibility APIs</a> so that assistive technologies can gather certain properties such as layout and bounds.</p>
+				<p>Like an element with role <rref>presentation</rref>, an element with role <code>generic</code> can provide a limited number of accessible states and properties for its descendants, such as <pref>aria-live</pref> attributes.</p>
+<p>However, unlike elements with role <code>presentation</code>, user agents expose <code>generic</code> elements in <a>accessibility APIs</a> when permitted accessibility attributes have been specified. User agents MAY otherwise ignore <code>generic</code> elements if such permitted attributes have not been specified.</p>
 			</div>
 			<table class="role-features">
 				<caption>Characteristics:</caption>