http://www.blackholes.org.uk/PP/oeb-819-1.pdf
There you go, that's the bulletin. Page 5, 3rd sentence down.
When the approach phase is activated, the characteristic speeds are recomputed using the actual weight and C of G
So the later you leave it the closer the speeds are calculated to your actual landing weight. But as I've said, 1 tonne makes 1 knot difference so don't get your knickers in a twist.