Your 100% right Ken, thats how carrier to carrier charters generally work.
But where talking about "in house" services here.
Do you know how many QF 600 series MEL-BNE MEL flights have operated as additional capacity required & the operating crew unaware that they were actually J* charters.
Any JQ charters operated by QF will carry 4 digit flight numbers. QF600 series MELBNE flts are not JQ charters. Some will however carry the JQ codeshare flt number.