I wonder if the SKF product is unconsidered because it is patented and mentioned in the prior art. The patent touts its usefullness "for supplying dry air to a storage facility" which is a different industry than the air brake industry?
I do not see the word desiccant in those references. Take a look at
Patent number us4673420 from 1987. I do not see it listed in the face of the patent in question so it is likely something the examiner didn't look at. It may not be seen as teaching the "inner chamber" of claim 1.