Sabudana granules (sago pearls | tapioca pearls) look like grains but they are actually a starch extract derived from cassava. Check out this article for details: Starch Extracts are not Whole Foods. As the name suggests, they are extracts. We may browse through a Reddit thread on this theme.
(13 mins, 2021) How Is Sabudana Made In A Factory
We may jump to offset 7:14 and watch for 2-3 minutes to see how sabudana is produced in an industrial setting by wet grinding, sieving (extracting starch in the form of a starch rich liquid) and drying.
(4 mins, 2022) Sabudana Making Process
Cassava & Cassava Flour
If we wish to follow the "Whole Food" part of Whole Food Plant-Based guidelines diligently, we may choose to avoid sabudana (a starch extract; not a whole food). Instead, we may buy fresh cassava (a whole food, not an extract) from grocery stores if it is available. We could also use cassava flour like this one at Walmart.