Can't help you with that one. I've noticed the occasional change, but never really wondered about it.
We simply get a zero fuel weight. There's no need for any more, unless we're doing a manual load sheet, and I don't think I've done one of those in about 25 years.
If I really wanted some weight off, to make space for fuel, I'd tell them how much I wanted, and it was up to load control to work out where it came from. They tended to start with the staff passengers....
