While + Past Simple + Past Simple vs. While + Past Continues + Past Simple

We can use these two tenses together as below, for example:

While she was walking on a sunny beach, Amy slowly read an extremely long book about justice.

I was wondering under what conditions we can use this structure, i.e. While + PS + PS:

While she was on a sunny beach, Amy slowly read an extremely long book about justice.

Solution 1:

This is a 'complex sentence' (that has a main clause and minimum one dependent clause).
The first clause is Past Continuous, and the second one, in Simple Past tense. This structure implies "when an action took place, the other was progressing."

Here, both clauses have a common subject. It is similar to "While watching the movie, I forgot the bus-timing."

This can better be written as, "Walking on a sunny beach, Amy slowly read an extremely long book about justice"; now it is a simple sentence (single-clause sentence).