In the New Testament and in Clement's letter to Corinth the two words name one office: presbyteros and episkopos are used of the same men in the same paragraph. A single bishop standing over a college of presbyters is first clearly visible in Ignatius, writing about 110, and even then he is arguing for it rather than describing something settled. So the earliest entries in every succession list in this dataset are being read backwards through an office that did not yet have that shape.
The Early Church · ch. 3