Well no, I wouldn’t think that’s the reason why WM and FF don’t share their test results. And I’d quite like to know what tests they did and what they found.
This might plausibly explain why others who do use DWR down don’t share results. On the other hand, maybe it’s never occurred to them to share the results because the results merely confirm what they think buyers believe – that DWR down is better.
As for the benefits being overstated, there is the test where the guy jumped into a frozen lake with his DWR down jacket and sat there, twice. He concluded that DWR down works so well that the only reason to buy synthetics is to save money. I think that’s overstated, maybe wildly so. (It’s been suggested in this forum (this thread??) that he merely tested the DWR coating of his jacket’s fabrics, and after reading the article again, I agree that there is no way to be sure any water got past the fabrics.) But even if some have wildly overstated the benefits, that doesn’t mean there is no useful benefit.
And yes, I hope FF and WM would jump on the band wagon if there is a great enough benefit. But if there’s a benefit that will be more valuable to some people than to others, and if there are also disadvantages that will impact some more than others, then what is right for FF and WM might not be right to me. Furthermore, did they do the right tests for the situations I’m concerned with (or for some other situations that customer X is concerned with). Who knows?
Really, if every reputable manufacturer said this stuff is no good, it wouldn’t make sense to second guess them. But when reputable manufacturers differ, I see no reason to be sure than WM and FF have determined and weighed the advantages and disadvantages for me better than the other manufacturers. When reputable manufacturers differ, we need better information to choose for ourselves.