Many of us have understood this for a very long time. One time at band camp... during a tech writing gig at a software company, I became the owner/editor of a 2,500+ page user guide. The problem with the guide was not the word count. It was a mix-mosh guide of feature-centered writing and task-centered writing. It rambled like a silly blog posting, moving the reader (if she cared to follow) along an unorganized path of inconsistency and failed heuristics.
When the revision was done, we had three information products: one user guide, one tech/fact sheet, and one compiled help file. All three brief, concise, and stylistic (if I don't say so myself).
The point: Brevity does not necessarily mean discarding information simply to reduce word counts. Nor does brevity mean a picture contains a thousand words. Brevity, for the technical communicator, means the most efficient and effective way to transfer knowledge or skills to user of the information product. If brevity improves retention and learning, that's icing on the cake.