How is the property alias feature used to select multiple nodes?

The last remark of section 8.2.6:

"Multiple nodes may be selected with this <vprop:propertyAlias> feature. However, those selections may be then filtered in the rest of expression and result in one node returned."

I cannot figure out what this means... I do not see how a query within a property alias may return multiple nodes, as it should conform with the type specified in the property. Further, the query should be evaluated the same way as a query in an assignment, according to section 7.3. In assignments a query cannot return multiple values.

Could someone provide an example of how the property alias feature is used to select multiple nodes?

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