Within hours of being indexed, the JavaScript on the page would have been executed and the links extracted. Presumably these particular extracted links didn't look particularly interesting to the crawl scheduling algorithm, and sat in the crawl scheduling queue for 16 or 17 days.

Source: I worked mostly on JavaScript execution in Google's indexing system from 2006 to 2010. I don't know the intricacies of the crawl scheduling, but I do know it's highly non-trivial.