Writing: Improving Sentences

<ol>
<li>The Red Cross workers had not expected the refugees from the flooded plain to be as desperate and as undernourished as those whom they (had seen) earlier in the week.</li>
</ol>

<p>Why is "had seen" correct? Shouldn't it be "saw" because it happened and ended in the past?</p>

<p>What’s the source of the question?</p>

<p>“had seen” indicates that the verb 1. has ended in the past
2. happened before another action</p>

<p>So would “saw” be correct?</p>