The spec should make clear that contacts with unknown presence shouldn't be added to the hashtable in reply of GetPresence. That happens if requesting presence for a contact which is not in subscribe list.
So, Presence is now deprecated. SimplePresence actually mandates the opposite: see <http://telepathy.freedesktop.org/spec/org.freedesktop.Telepathy.Connection.Interface.SimplePresence.html#org.freedesktop.Telepathy.Connection.Interface.SimplePresence.GetPresences>.
What was the rationale for your requested clarification?
Not going to fix this without a rationale, or in that interface in any case.