Jetstar - Seoul-Sydney-Melbourne Transfers

[moa999]

Is that just a security checkpoint to enter the sterile departures zone or full transfer with airline desks like you see in hubs?

Believe it's just security, so you need a boarding pass, which will probably be the deciding issue in ICN for the OP.
JQ48 arrives 9am so I'd expect the area to be manned at that time.