You have to be careful when trying to analyse isolated sentences like this. A key part of understanding how tenses are used is seeing how they relate to the way that surrounding narrative events are presented. Where did you get these sentences, and who told you that the past perfect was the correct form?
During the ongoing coronapocalypse, students in Poland have lessons online. This is an actual test used in public schools in Poland, and students are marked for their answers in this test. I also found it online, after a group of students asked me for help with understanding their "mistakes" they received a bad mark for.
I'm biased and I know it, but it pisses me off that students are punished with bad marks for doing something that native speakers do on a daily basis, without anyone noticing.
I'm a scientist. I value the scientific method. English is a language for me, not a school subject. Languages exist in the world, whether we like it or not, and the job of a linguist should be to look at a language, try to figure out how it works, and describe how it works so that others can understand it, similarly to, say, physics, that exists in the world whether we like it or not, and the job of a physicist should be to look at it, figure out how it works, and describe how it works so that others can understand it. If a physicist comes up with a set of rules that ought to describe how physics works, but that set of rules doesn't match reality, it's the physicist that is wrong, not physics itself, as a natural phenomenon. I think the same should apply to language and languages. Schools should teach how (a) language works, not make a "school subject" out of a living language, with a set of rules that doesn't match reality, and punish students for not obeying these rules.
As for the word
rules, I used this word because that's how students are taught and how they perceive what they are taught - a set of rules they need to follow when taking an exam they're going to be marked for. They're taught to, say,
always use the past perfect for action a if action a precedes action b while both a and b are past actions. They are taught they are going to be punished with a bad mark for not obeying this rule. That's the rule they have on their mind when they're taking a test, with the fear of being punished if they don't follow it. They later remember that rule when actually using the language in the real world, and see it collide with how actual living people use the language. I'm one of such students, just 10 years later.
Side question: in post #12 I said:
"There are situations in which I think I can use either, and I'm sure nobody would notice the difference unless they were actively scanning for it, or
were trained to spot it."
Would it be correct to say...
"There are situations in which I think I can use either, and I'm sure nobody would notice the difference unless they were actively scanning for it, or
had been trained to spot it"
...instead? I think I can feel the difference in meaning.