You're property is either a residual property (it corresponds to one of the property definitions named "*" on nt:unstructured), or it's a non-residual property on another mixin, which must be joined. So, yes this is the expected behavior. But you could file an issue to provide a more useful/meaningful error message. We could even try to improve our handling to be a bit smarter about how we're processing the query.
BTW, "SELECT *" can never be expanded to include residual properties, so the way around this is to always specify the properties you want in the select clause. This is considered a best-practice (and is a best practice of SQL applications, too). See this section for a treatment on this topic.
OK. Thank you.