Is is possible for Salesforce Duplicate Management matching rules to compare across objects?  

This article talks about cross-object duplicate rules:

as does this Salesforce help page:

This article shows how to make them:

but it doesn't match what I see in the Salesforce matching rules screens.

When setting up matching rule criteria, there appears to be no way to select anything other than a field from the current object.

Is this a feature that needs to be enabled somehow or that existed and was withdrawn?