According to you, does <xs:include schemaLocation="" /> in an XML schema document means, that it is an include of the including schema (i.e it is a recursive XML schema include)?

I think otherwise, i.e I guess  <xs:include schemaLocation="" /> means an include of a null schema reference, and hence <xs:include schemaLocation="" /> should be ignored by an XML Schema validator. Please correct me, if I'm wrong.