Consider the following:
<b tabindex="0">foo</b>
Because it is focusable, it has to have an accessible object (i.e. be mapped) so that accessibility events can be emitted.

Likewise: <b title="hello world!">foo</b> would need an accessible object because otherwise there's no way to expose and associate the title value.

At the present time, the HTML-AAM lacks language/mapping for a number of inline elements. There should be either language (a normative note) or mappings for how to expose "not mapped" elements which must be exposed due to attributes.

As for what the mappings should be, a quick glance makes me think that the content for "a (no href attribute)" is the expected result for all platforms for the sorts of things I've described.