Знатокам английского. Объясните, пожалуйста, почему в придаточном предложении Past Simple (попытка 2)

Ты прав в одном - нельзя циклиться на правилах! А если правила необходимы, то лучше их читать не в переводе на русский. Надеюсь, разберешься в том, что написано ниже, а если нет - спрашивай - переведу на русский.

В данном случае Simple Past потому что присутствуют When-clauses.
He cried out in pain "as(when) the nurse gave him an injection". или "As (when) the nurse gave him an injection", he cried out in pain.
He gave an exclamation of joy "when the bank manager agreed to lend him the money". или "When the bank manager agreed to lend him the money", he gave an exclamation of joy.

When-Clauses Happen First
Clauses are groups of words which have meaning but are often not complete sentences. Some clauses begin with the word "when" such as "when I dropped my pen..." or "when class began..." These clauses are called when-clauses, and they are very important. The examples below contain when-clauses.

Examples:
When I paid her one dollar, she answered my question.
She answered my question when I paid her one dollar.

When-clauses are important because they always happen first when both clauses are in the Simple Past. Both of the examples above mean the same thing: first, I paid her one dollar, and then, she answered my question. It is not important whether "when I paid her one dollar" is at the beginning of the sentence or at the end of the sentence. However, the example below has a different meaning. First, she answered my question, and then, I paid her one dollar.
Example:
I paid her one dollar when she answered my question.

А Past Perfect предполагает, что одно из действий произошло позже другого и не обязательно как следствие первого.
For example:

I vent to bed after I had finished my homework.
First: I finished my homework. Then: I went to bed.

The past perfect verb tense is used:

to state "how many"

to clarify the order of two past non-continuous events

to state a past action was completed before an other action

Согласование времён

скорее всего одновременность действий. просто perfect употребляется когда во времени большой разрыв. тут он совсем ни к чему.