p:xquery and c:data

The text in 7.2.9 (p:xquery) says this about the document on the 'query'
port is handled:

"If the document root element is c:data or has a c:content-type
attribute that specifies a text content type or a media type that the
implementation recognizes, then the text descendants of this element are
considered the query."

So, does this really mean that the p:xquery step always takes the c:data
text content no matter whether what c:data/@content-type says?
Consider this:

<c:data content-type="image/png">iVBORw0KG...</c:data>

Or was the original intention to say that the content type (specified
either by @content-type in the case of c:data or by @c:content-type in
other cases) must be a text content type (or anything else the
implementation recognizes)?

Regards,
Vojtech