Wingspar, the MOU is based on group seniority starting in 2004.
MOU seniority numbers in Qantas (~2004) are not senior enough for widebody FO, whereas all eligible JQ Pilots (former Impulse pilots, <2004) are Captains, mostly on the 787.
This 'one-sidedness' is purely a result of rapid expansion in one carrier, and stagnation in the other.