accessModeSufficient can be set to visual

Hi DAISY

I have a few questions after reading though the pages describing accessMode and accessModeSufficient on the KB.

The definition of textual contains this sentence - "If a publication contains images of text, the visual access mode is also set (or set instead, if the publication only contains images of text).” - which indicates that an accessMode value of _visual_ is sufficient to describe a publication that relies on the visual sense.

With accessModeSufficient defined as “a list of _single_ or combined access modes that are sufficient to understand all the intellectual content of a resource”, it seems that by entering a single entry of _visual_ the accessibility requirement can be declared.

And it might follow that adding only a visual accessMode and accessModeSufficient to a complex fixed layout EPUB document, even one that doesn’t necessary have text as images, would mean that they are declaring that they are accessible but require the visual access mode? e.g.

```
visual
visual
```
Doing so passes ACE with no wcag2aa or EPUB violations.

Is this a loophole that is open to abuse and needs to be closed?
Or is it a legitimate use of schema.org accessibility metadata to identify the accessible qualities of a visual only publication?