Of Papias and Polycarp

Papias and Polycarp are said to have been contemporaries of each other.

Eusebius in the 4th century, corrects Papias in his assertion that he knew John the apostle. It is disputed which John that Papias knew.
Christians of the 4th century couldn’t identify which of the four Johns (John the apostle, John the elder, John of Patmos or a John with a combination of any of the previous identities) that Papias knew — how can someone 2000 years later claim to make that identification for Papias’ contemporary, Polycarp?

Polycarp himself not once quotes or references John the apostle in any of his extant writings.
Iraeneus, who in the late second century, recorded the claim that Polycarp knew John, heard this in his childhood.

There are literally no other sources which can corroborate something that Iraeneus writing in the late second century, claims to have heard in his childhood, much less so from any of the extant writings of Polycarp himself.