According to Guidelines 188.8.131.52 (Personal Relationships), <listRelation> and <relation> are purportedly both members of att.typed. However, only <listRelation> is. <relation> should be made a member of att.typed.
This looks like a corrigible error to me. In olden times, @type was locally defined in cases where the Guidelines wanted to propose some specific set of values. This is no longer necessary, and in any case, the list of values proposed here is fairly unhelpful. Unless anyone objects I propose to fix this for the next release.
Fixed at [r12953]