I don’t think it is, but the concept doesn’t seem incoherent.
If a conceptus is an actual person, and becomes so at the moment of fertilization, isn’t there *something* that pre-exists it that has the potentiality?
1 There are actual persons
2 Some of these actual persons came into being
3 ∴ there must have been something pre-existing that was actualized as a person
4 Whatever that was, was a potential person.
5 So there must be potential persons.