Sometimes HN admins revive quality posts that didn't get much traction when they were first posted. When this happens, the timestamps are updated to make the post look new.

I can't say for sure whether this is what happened here, but it is a possible explanation.

This post did in fact go through the second-chance pool: https://news.ycombinator.com/pool

(For more details on posts getting “rescued”, see Dan’s comment here: https://news.ycombinator.com/item?id=11662380)