With that many downloads, we'd expect to see an increase in the percentage of Safari users on other sites. So, it'll be the many sites that catalog that information that will be the real proof in the pudding. By advertising early, the article speculates Apple is trying to encourage other companies to adopt support for it:
”... Apple apparently hopes to light a fire under companies like Yahoo to make Safari 3 support a high priority. Fast adoption among Windows users is key to driving support by Web companies. "If they can successfully do that (show strong adoption) than they become a more viable platform because of it, and Yahoo and other developers will probably make their platforms compatible," Baker said.”
You can read Apple's press release over this at their site.