I agree with what is written in these two paragraphs from that page:
"If the Past Perfect action did occur at a specific time, the Simple Past can be used instead of the Past Perfect when "before" or "after" is used in the sentence. The words "before" and "after" actually tell you what happens first, so the Past Perfect is optional. For this reason, both sentences below are correct.
- She had visited her Japanese relatives once in 1993 before she moved in with them in 1996.
- She visited her Japanese relatives once in 1993 before she moved in with them in 1996.
If the Past Perfect is not referring to an action at a specific time, Past Perfect is not optional. Compare the examples below. Here Past Perfect is referring to a lack of experience rather than an action at a specific time. For this reason, Simple Past cannot be used.
- She never saw a bear before she moved to Alaska. Not Correct
- She had never seen a bear before she moved to Alaska. Correct"
You will hear some people use the past simple in cases like that, but the past perfect is better, in my opinion.
- For Teachers