Is basically whats in the link and the email I got from WM
"Thanks for your email. This might be a lot more info than you bargained for when you asked the question about treated down.
Currently we do not offer any bags with hydrophobic treated down because as of today we still have no compelling evidence that it provides better overall performance throughout the life of our product. We have been testing treated hydrophobic down from three of the major industry suppliers (i.e. DriDown, DownTek, and ResistDown) since December 2013 but nothing has prompted us to strongly consider using it in our products based on the collective feedback from the tests thus far. Our plan it to continue testing for long term performance comparisons but up to this point we have been underwhelmed. Comparing any of the treated down with our goose down is like comparing at the fresh powder snow in the backcountry to the slush in the parking lot of a ski resort. We currently don't have plans to use hydrophobic down in the near future.
We have done quite a bit of testing and due to multiple factors we have seen little performance difference between our down and hydrophobic down. A few of our tests have involved sending out sleeping bags and jackets that were cut in half and have one half hydrophobic one half normal down. In every case users where unsure which was which or if there was a difference at all. These samples were used for months at a time, some of them for nearly a year straight. We believe this is because of the water resistance and breathability in our shell technology.
Secondly there are numerous concerns with the fill power testing of hydrophobic down. When down is tested for fill it goes through a drying and conditioning process. This process is a standardized comparison but is not at all indicative of real world performance. Hydrophobic down artificially raises the fill count due to this drying and conditioning. For instance, we conducted a test where we got 2 samples from the same batch of down, one treated and one untreated. The supplier claimed that the batch was 850 fill. The treated came out around 860 but the untreated sample came out at ~700. In real world conditions both of these samples would perform around 700 or even lower depending on humidity. Using down that isn't as lofty as we claim it to be is misleading and leads to lower real world performance.
Third is that most down, and especially our stuff, has good natural water resistant properties. Our down is thoroughly cleaned, but the natural fats and oils from the geese stay on the plumage. Though we know these fats and oils come off over time due to laundering and washing we have seen that they last a long time, and potentially longer than a hydrophobic treatment which also washes off. This is still unsubstantiated but our testing seems to indicate this trend especially as many hydrophobic treatments need retreating after only a handful of washes.
The natural properties of high quality goose down are amazingly resistant to water without any treatment at all. We have had samples of down floating at the top of the water in a container for over three months, even stirring it occasionally. When that level of natural resistance to water is paired with a breathable laminated shell fabric such as Gore Windstopper the result is a sleeping bag that you can float on water for a half hour or more, shake it off for a few seconds and its ready to sleep in immediately. No treated down, just quality shell materials and super nice pure goose down.
Thanks,
Ellen"