I can tell you one key sentence from his post is "reports what I believe is the largest publicly disclosed effort of this type", where the key words are "public

I can tell you one key sentence from his post is "reports what I believe is the largest publicly disclosed effort of this type", where the key words are "publicly disclosed". From talking to pharma companies, they all have done virtual screening with larger libraries than what is reported in this paper. I'm not familiar with details of Novartis's efforts, but based on talks with other companies, I would not be surprised if Derek is familiar with virtual screens at Novartis that have been 1-2 orders of magnitude larger. Many of the questions in virtual screening of large libraries are not answered in the paper as the authors did not look at them. As mentioned in the comments, they are using Enamine RealDB which has been around for a while, and Enamine has an even larger virtual library called RealSpace.