bindItems and SOM

I am trying to bind a drop down list (choiceList) to a list of records in my data set. My original XML looked like this:

<bindItems ref="$record.parent.People.Person[*].Identifier.Name" labelRef="$" valueRef="$"/>

But it returned no values. I played around and with alternative ways of getting my data, and settled on this:

<bindItems ref="$data.root.People.Person[*].Identifier.Name" labelRef="$" valueRef="$"/>

But what is weird is that within a scripting context:

xfa.record.parent.resolveNodes("Ballot[*].BallotIdentifier.BallotName")

Works just fine. Do SOM expressions not support the parent property in a bind context?