This probably comes back to aircraft doing a fairly tight turn at ORD, and what is likely the lack of gate availability in Terminal 1 for additional wide-body departures. ANA and LH depart from Terminal 1, but the ANA plane appears to be on the ground for much longer. However, the LH flight to FRA has about a 3 hour turn so clearly not impossible to arrive T5, tow over to T1 and depart from those gates.
LH departs out of the high B gates with a 748, so clearly they could fit a 789 there. The UA widebody gates in C would probably all be occupied for the NZ27 departure time as European flights go around that time.