There is no confusion here. Either a person is baptized in the eyes of the Church oir (s)he is not. The Nicene Creed says "I recognize one Baptism for the remission of sins." We repeat this every Sunday.
The Orthodox Church determines if a particular Catechumen was baptized or not. If it is determined that he or she was baptized but that the Mystery of Baptism is incomplete, it is completed by Holy Chrismation (anointing with oil).
The Orthodox Church has been practicing this for more than the last 1600 years. By the way, the same formula (Hoy Chrismation) is applied not only to Oriental Orthodox converts, but to Arians. It is a formula for those who once belonged to the Church but became heretics. For historical and political reasons, at one point, the Catholics were denied Holy Chrismation (confirmation) and re-baptized. Some still do, depending on how an individual received baptismal Mysteries (sprinkling or immersion).
For those who have never been in the Church (i.e. Protestants), Baptism is almost a given, since they are considered never to have been baptized (i.e. received any Mysteries, even if deficient) for all the good theological reasons stated by Calvin.
Concur. The question is whether or not the individual has, in fact, been Baptised ... and what to do if due to poor recordkeeping or dubious theology there's no certainty in the case.