she had grown up in Japan.

[Maybo]

Ms Shiino had announced in Instagram earlier last year when she received Japanese nationality, saying that she "may not look Japanese", but her mind had "become Japanese" because she had grown up in Japan.

Source: Ukrainian-born model winning Miss Japan re-ignites identity debate by Shaimaa Khalil, BBC

The writer used the past perfect tense for "had grown up". Is it because the grown up happened before she made the statement?

 

[emsr2d2]

Ms Shiino had announced in Instagram earlier last year when she received Japanese nationality, saying that she "may not look Japanese", but her mind had "become Japanese" because she had grown up in Japan.

Source: Ukrainian-born model winning Miss Japan re-ignites identity debate by Shaimaa Khalil, BBC

The writer used the past perfect tense for "had grown up". Is it because the grown growing up happened before she made the statement?

It's a type of reported speech.

What she (probably) said: "I may not look Japanese but my mind became/has become Japanese because I grew up in Japan".
Reported speech: She said that she may not look Japanese but [that she] had become Japanese because she had grown up in Japan.

Do you know about backshifting?

 

[Maybo]

Do you know about backshifting?

I think I finally got it! I sometimes don’t know how to differentiate “a past event happened before a past event “ or whether they’re using a reported speech.

 

[Tarheel]

Context. I was going to say "grew up in Japan" would be more natural to me until I read the article. It's perfectly phrased for that context.

Does she look Japanese? No, but I guess that's for a different discussion.