Let’s take a closer look at the first sentence you presented:
“NASA said the last time a space rock as big as 2005 YU55 came as close to Earth was in 1976.”
Note that there are actually two comparative phrases in that sentence. The first comparative is “a space rock as big as 2005 YU55” and the second, “came as close to Earth was in 1976.” These two comparatives are independent of each other; in fact, we can say that each has a grammatical life of its own. (By the way, the comparative “came as close to Earth was in 1976” is actually an ellipted—streamlined and made concise—form of the comparative “came as close to Earth as this time was in 1976,” so formally, there should be four “as’s” in all in that sentence). There’s no rule in English syntax that forbids the clustering of three or more “as’s” in a sentence, so we have to judge such grammatical situations on whether they make sense or not. I think you’ll agree that the sentence in question makes sense.
Now regarding this sentence from a news website:
“A Russian court ordered a maternity hospital to pay two families about $100,000 apiece for mixing up their newly born daughters 12 years ago.”
The use of the adverb “apiece” in that sentence in the sense of “each” is grammatically correct. By definition, “apiece” and “each” are freely interchangeable. The choice is a matter of style.
Now, regarding this question of yours: “Should it just be left to a reader’s understanding that the newly born daughters belong to two families and not to a Russian court?”
No, I don’t think so. In journalism, we should not leave such things to chance. I think the reporter and editor of that news story were very well-advised in making it absolutely clear that it was the maternity hospital that had mixed up the two newly borns. It just so happens that in the process, the phrasing of the sentence also makes it crystal clear that the newly borns belong to the two families and not to the Russian court. We should appreciate the phrasing of that sentence rather than find fault with it for doing that.
