Jan van den Hemel writes: In the previous video we explored how to add details without using booleans. However in some cases, you can see some shading artefacts where objects overlap (also known as “Z-fighting”). To solve this, we use one more modifier. Then things look perfect!
from BlenderNation https://www.blendernation.com/2021/10/12/add-seamless-details-without-booleans-part-2-data-transfer-modifier/