What causes HN post relative age vs. timestamp discrepancy?

Looking at the HN front page, some human-readable age labels ("10 hours ago") correspond with timestamp in title attribute

    10 hours ago
    (provided now = 2023-10-02T13:11:33)

but others are off, sometimes even by days.

For example current front page, archived "2023-10-02T09:36:17" [1] features post

    Astronomers discover thousands of red galaxy hearts with powerful radio signals
    4 hours ago (title="2023-09-29T15:07:25")

"4 hours" ago would be something in "2023-10-02", but title timestamp goes two days farther. (Skimmed output of makeshift browser dev tools console analytical script [2])

Is it intentional?

[1] http://web.archive.org/web/20231002093617/https://news.ycombinator.com/news

[2] https://gist.github.com/myfonj/7c551e381e3a03362b7e4c92d4c8120d