The default layout is not a must. Airbus has stated that the configuration could be changed, and those changes are on offer. We don't put 800 because that number of passenger is simply not certified.
There is no such thing as "default" layout. Those layouts are there purely for marketing purpose. When it comes down to it, the airlines each have their own standards, and each piece of equipment comes with a price tag.
Reason why we use 2-class configuration for A330's is as you have stated. We have not been able to find the one class pax number.
It is not that we do not appreciate your efforts. However, the information you have provided does not match the criteria we use for our database.