See https://chat.fhir.org/#narrow/stream/179255-questionnaire/topic/Variable.20name.20uniqueness

The part of https://build.fhir.org/ig/HL7/sdc/expressions.html#variable that talks about the restrictions on variables names (particular with regard to other variables in the form) needs to make it clear that you can have two variables with the same name in the same Questionnaire as long as 1) they are not on the same node and 2) one is not on an ancestor node of the other.