Google will sometimes show results from Reddit but ultimately link to a different post. AFAIK, the content that Google says is on the page may actually be content that is either from related posts shown on the Reddit mobile site or from another post somewhere on the subreddit (or maybe just somewhere else on Reddit entirely?). The timestamp that Google gives seems to be from when the linked post was made (with some discrepancies as to when Google and Reddit decide to round up or down in terms of unit time)
Edit: I just searched for “Planck” on Reddit and immediately found this post, posted a couple hours before the Fediverse post
Edit 2: a commenter had almost the same exact line of thinking that I had lol
Re: your edit
Google will sometimes show results from Reddit but ultimately link to a different post. AFAIK, the content that Google says is on the page may actually be content that is either from related posts shown on the Reddit mobile site or from another post somewhere on the subreddit (or maybe just somewhere else on Reddit entirely?). The timestamp that Google gives seems to be from when the linked post was made (with some discrepancies as to when Google and Reddit decide to round up or down in terms of unit time)
Edit: I just searched for “Planck” on Reddit and immediately found this post, posted a couple hours before the Fediverse post
Edit 2: a commenter had almost the same exact line of thinking that I had lol