I downloaded the source code of Lurie's paper paper and compiled the TeX file. The date shown on the first page is today's date (inserted by default via the "report" documentclass commandsince no date is specified). So this would confirm Andy Putman's suggestion that April 1, 2019 is the date the paper was last compiled byat arXiv.org. ArXiv removes compiled versions of papers after some time, so apparently this paper from 2008 had not been accessed recently.