If Bernard Dubourg is correct that Paul/Shaul is only a symbol for the Sheol and its reaction to the resurrection of Jesus, then the same descent to Capernaum (=Hades for Heracleon) may assume a new meaning as a descent on Paul himself.
This may explain also why Marcion had the descent to Capernaum in the incipit: the first apostle to receive the true Jesus on the earth was Paul himself!