It's a common strategy in any industry to announce a high number of orders when introducing a new standard. And by many aspect, a new a/c is a new standard, with many complementary goods coming in (think of engines, spare parts, galleys, equipments and so on).
Think of the video game console industry. Everytime a new player comes in (whether
MS, Nintendo, or Sony), they do their best to make people think their console has already been pre-ordered by many customers. So that potential customers are ensure they'll get enough complementary quality complementary goods (games) and enough partners to play with (other customers).
It's the same in the airline industry. You don't want to buy a product that only ANA (with a strong political influence), and two minor charter European carriers have purchased. So, it's Boeing best interest to overstate the number of orders they got, so more airlines comes in.
Communication is Success