(DISCLAIMER: Answer based on observation, rather than hard fact...)
FWIW, I've noticed similar discrepancies with other reported "news" articles as well in the SERPs (you are not alone). The same URL is linked to in both the "Top stories" section and the regular search result, but there is a small discrepancy in the timing. If there is a difference, the "Top stories" section shows the lesser time. Sometimes this difference might only be 1 minute (if less than the hour).
This isn't actually too difficult to replicate. If you search for the title of a news story (without quotes in my example) and after a few searches you often find one that shows this discrepancy.
For example, if I currently search for
UN commits to stop ocean plastic waste (no quotes), then the top result returns a BBC News article. The "Top stories" section reports "20 hours ago", yet the search result below (for the very same URL) shows "21 hours ago".
I think @StephenOstermiller's comment is relevant:
Google has different systems that get notified about updates differently.
It may also just be down to how the different systems round the time for display. For example, take the news article above... examining the actual time in the article (
data-seconds property of the HTML element) shows that the article was in fact updated 21.86 hours ago. From that, you could assume that the "Top stories" section always "rounds down" and the search results are "rounded the nearest whole number" (just an observation)?
UPDATE: In fact, performing the same search a few minutes later (in the next "hour") shows how the time is updated. Now the two
bbc.co.uk URLs (previously showing "20" and "21 hours ago" respectively) both show the same "22 hours ago". And the
ladbible.com URLs (2nd result) that previously showed the same "15 hours ago", now show two different times (1 hour difference): "16" and "17 hours ago" respectively. This would seem to be consistent with simply a difference in how the time is displayed (ie. rounded), as mentioned above. (?)