Used CWT fuel yesterday, 9 hour freighter flight. Very close alternate. 6 tons in the CWT. That being said, the payloads are usually pretty heavy and the CWT is so big that I can see why the stab tank would not be used very often as you mentioned. But some flights can be quite long. Thinking of Singapore to the US. I suppose it is cheaper to fuel up enroute with the bigger payload than cut into payload for longer range.
Were stab fuel tanks ever a freighter option or never offered. And it appears that converted freighters have had their stab tanks removed.