How do you know that? Seatmap are not a reliable indicator - I made this mistake once to board a full flight to India (idea was to save on assigned seat) - many people booking will not be assigned a seat until checkin. The information your OTA or bespoke corporate travel agent has is no different to expertflyer, seatmap bad indicator and for availability you'll only see a max of 9 in each bucket..
Empty transatlantics aren't unheard-of. I was one of only two passengers on a Lufthansa MUC-EWR last year.
It's better for them to run highly unprofitable flights than miss their contract obligations with big corporations that want a plane available to move people transatlantic on a day's notice.
