The value of a style:data-style-name attribute is required to match the name of a data style.
We don't say what happens if it doesn't match the name of a data style.
Moreover, we don't have a similar "must" condition for other instances of attributes with styleNameRef values.
1) Make it mandatory that all attribute values of type styleNameRef match a style of the appropriate type, and
2) Define what happens if an attribute with a value of type styleNameRef fails to match an existing style of the appropriate type?
Being mindful that the question of when the style must exist is an issue. In other words the creation of the reference may come immediately before the creation of the style. Is that OK?