In GMAT, there are some grammar rules that cannot be flouted and there are stylistic guidelines that are optional. Use of past perfects when the timeline is explicitly made clear with the use of earlier, after, before or mention of sequential years falls into the second category. GMAT itself is not as fastidious about this as some of us tend to take it as gospel.
Look at the following examples.

Retailers reported moderate gains in their November sales, as much because of their sales of a year earlier being so bad as that shoppers were getting a head start on buying their holiday gifts.

(A) of their sales of a year earlier being so bad as that
(B) of their sales a year earlier having been as bad as because
(C) of their sales a year earlier being as bad as because
(D) their sales a year earlier had been so bad as because
(E) their sales of a year earlier were as bad as that

OA: D.

For at least two decades or more previous to when the Venetian artist Giovanni Battista Tiepolo died in 1770, he was the most admired painter in Italy.

A. For at least two decades or more previous to when the Venetian artist Giovanni Battista Tiepolo died in 1770, he was
B. For at least two decades before the Venetian artist Giovanni Battista Tiepolo died in 1770, he had been
C. For at least two decades or more before the Venetian artist Giovanni Battista Tiepolo's dying in 1770, he had been
D. When the Venetian artist Giovanni Battista Tiepolo died in 1770, for at least two decades previously he was
E. When the Venetian artist Giovanni Battista Tiepolo died in 1770, having been for at least two decades before that

OA B

She was less successful after she had immigrated to New York compared to her native Germany, photographer Lotte Jacobi nevertheless earned a small group of discerning admirers, and her photographs were eventually exhibited in prestigious galleries across the United States.

(A) She was less successful after she had emigrated to New York compared to

(B) Being less successful after she had emigrated to New York as compared to

(C) Less successful after she emigrated to New York than she had been in

(D) Although she was less successful after emigrating to New York when compared to

(E) She had been less successful after emigrating to New York than in

OA C

The question under discussion also can be taken as one more such example. It might be prudent for us not to make or break a choice on the use of past perfects on this ground.
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VeritasKarishma GMATNinja
ChiranjeevSingh
Why option d is wrong

Having + verb is also used to denote that some action completed before another action completed

Posted from my mobile device

I wanted to ask about option A which has "which itself". isn't itself redundant here? which had been adopted earlier would have been correct sentence. please advise.

Perhaps Utkarsh, but I would like to draw your attention to the fact that all the 5 options use itself. So, redundancy (if at all there is any), is clearly a non-issue here.

The reason I highlight this, is because test-takers do need to develop an eye for quickly figuring out the differences in the five options, so as to evaluate what really matters for that question.
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