cxorcist,
That document supports what I said, there is no common type rating between the 777 and 787 under the FAA system. As I said, talk to any of the United guys and ask what is printed on their licence, it is B-777;B-787. The common type rating between the 757/767 is B-757/B-767. Once trained on B-757, no additional training is required to have the B-767 type rating.
The short course at United from the 777 to 787 is 16 days (around a month). The FAA does not issue a 787/777 type rating, it is 777 and there is 787, no dual rating.
This is essentially the same as a 330/340 CCQ, that is not a common type rating.