Syntax and Primer: URI for XML Schema

Why do the Primer and Syntax docs both use:

 http://www.w3.org/2001/XMLSchema# ...

as the base URI in the examples of rdf:datatype usage?

Rather than perhaps:

 http://www.w3.org/2001/XMLSchema-datatypes

which Syntax uses in the RELAXNG Compact Schema?

Thanks,

Art Barstow
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