I don't think the tank is being removed. It holds 9.8 tonnes and it's integral within the stabiliser. I suspect the pumps valves and pipes are being removed to save a bit of weight. The 744 freighter doesn't have a stab tank, the 744 BCF is being configured accordingly.
This is because the freighter carries much higher payloads than the pax version. Fill a 744 with fuel, you can fly from Hong Kong to Europe, but with only about 60 tonnes of freight. To carrry the max 110 tonnes of freight, you will only get as far as Dubai, but staging makes economic sense.