The 767 and 777 have the same characteristic. I’ve seen the 767 and 777 totalizer fuel versus FMC calculated fuel drift apart by as much as 800 to 900 kilos by mid-flight, at which point the two values start to drift back together so that by TOD they become very close. If memory serves, wing-bending is the culprit but perhaps TD can weigh in on this.
As to your FOD dropping, on the Boeings (at least when I last flew the 767/777/787), the SOP was to not load the arrival/approach until sometime prior to top of descent, whereas on the Airbus, we’d load the whole shebang from takeoff runway to approach at destination. Obviously the Boeing method will result in, depending on the airport, a substantial decrease in fuel over destination once the arrival is loaded. At airports like PEK or PVG I’d typically see as much as 1,500kilo decrease in FOD.