A.'Past perfect is used to give background information',a grammar book teaches, and provides a task- introduced by a model example-in which one should use either the past perfect simple or continuous.Here is the model example:

1.From young age,Hinault was dedicated to his training programme.(always/want/be/cyclist)
And the background information becomes:He had always wanted to be a cyclist.

In the above sentence it is clear the the continuous can't be used.

My inquiry is a bout the following sentence:
2.After retirement he started writing books.(learn/many things/during his career)
Background information:He had learnt many things during his career.

How can I explain to my students why they used the past perfect simple and not the continuous-as in the Answer Key?

B.I need some help regarding how I can get through to my students the the meaning of background information and justifying using the past perfect simple or continuous in a simple way.

Lots of thanks.
Ugh. Nobody needs to learn that stuff until they are fluent and can do it themselves if they are so inclined. What a waste of student energy!

Past continuous forms supply background durational activity for another action (usually an 'instantaneous' one). In #2, the man was retired; he had finished 'learning'; therefore, that activity is not background (i.e. contemporaneous co-action) to his writing of books. Ergo: past perfect 'simple' is needed.

Thanks for the explanation.

I know it's a waste of student energy, but the material is in the book, and the students always want to know 'Why?';even when things are axiomatic.

Thanks, again.