Actually I was thinking they were the fork and shock off of a '99/'00 RM. The 49mm forks on the '99/'00 are twin chambers, so that would qualify for the "sealed and pressurized" portion. I bet they went to Showa and had them build them to their specs instead. Jeez, for $4500 you could by a used RM and sell the rest of the bikes for parts!! That suspension has a ton of potential.
I believe that the chamber above the base valve is sealed and pressurized. This chamber is normally open( on a production bike)to the outside chamber.
I would have to say that they close it up and add a slight nitro charge.
Remember this area is normally vented to the outside chamber and it would receive a positive pressure once the forks start compressing.
By sealing this area, the outside chamber would have zero impact on the inner chamber.
Maybe this is the effect thay are after in some sort of performance gain.
Take Care, John