Boyington,
Thanks. I think I can see what you are missing.
1)
This gives the impression (at least to me) that what is given in the QRH is the ceiling for twin engine
Title of page = One Engine Out.
2)
whereas the checklist in the FCOM states with a precondition (Black Dot)"If Wing A/Ice off ....
It sounds like you have never opened the X Bleed valve in the sim with Eng Fail No Damage.
If X Bleed is opened, then ECAM asks you to turn on the 2nd Pack. Thus the running engine is supplying 2 packs. The QRH Ceiling graph "One Engine Out" assumes only 1 pack.