Microsoft 365's eDiscovery Content Search operates independently of SharePoint's crawl index. It searches content directly within supported data sources, including SharePoint Online sites, without relying on the existing search index.

If you exclude a SharePoint document library from being crawled, it will not appear in SharePoint's search index. However, since eDiscovery Content Search does not depend on this index, excluding a document library from crawling does not prevent eDiscovery Content Search from accessing and searching the content within that library. Therefore, eDiscovery Content Search can still locate and retrieve items from the excluded library.