As I qualified, they're referring to the 5 speed hub that was used on Brompton bikes prior to Sturmey Archer going bankrupt, so yes, the BWR 6 speed would be lighter than that. But the new SA five speeds are lighter than BWR 6 speed setup by approximately 60g.

Look here:
http://www.sturmey-archer.com/userfi...99-English.pdf
The Sprinter 5 speed is listed as 1.2kg. The BWR hub plus extras would come to 1120g, so it's significantly lighter (80g). But current 5 speed hubs are 1060g, so they're somewhat lighter than the BWR.
This means that a 10 speed setup based on a S-RF5 would be 120g heavier than a 6 speed. 1240g for 10 speeds is pretty good, I think.

There's a massive difference in weight with any other multi-speed hub option I can think of, i.e. a X-RF8 is a whopping 1770g, 650g heavier than a BWR 6 speed setup. Alfines are actually heavier than I'd previously thought, again adding a chunk of weight.