Accoreding to XSLT 2.0, the way in which the base output URI is established is implementation defined. In the absense of a supplied base output URI

"A base output URI. [Definition:  The base output URI is a URI to be used as the base URI when resolving a relative URI allocated to a final result tree. If the transformation generates more than one final result tree, then typically each one will be allocated a URI relative to this base URI. ] The way in which a base output URI is established is implementation-defined."

Thus I believe that fn-transform-err-10, 11 and 12 which are attempting to exploit an unset base-output-uri are testing implementation-defined behaviour.