All science-fiction ends up being "set in the future of an alternative history" after enough time passes by, that's pretty much a given.

However, the alternative history as given in a sci-fi book tends to be relative to the time period the author wrote it in - by not having technology that is ubiquitous now, by continuing a belief or view that is considered outdated now, by involving the Soviet Union colonizing Mars, by depicting a United Nations that quickly turned into a world government as Clarke does in "Childhood's End", whatever. As such, the depiction of 2100 in the books of a writer of the 1950s can feel dated.

Now, you argued in your review that this was not the case, and Tom disagreed. I didn't see him saying anywhere that it "invalidated" the book for him, merely that for him personally, this particular indication of when the book was written made it seem very dated, whereas for you evidently it wasn't a big deal. It's not about "anomalies", either. It's about how the indications in this book about what time it was written in were not particularly obvious to you, so you said it hadn't aged, but were obvious to Tom and so he said it had.