Currently "full text" is limited to first 65K characters of an article or of a complete [!] book (along with chapter abstracts only) from CDI, or even less from Alma, and not from all sources (e.g., not from JSTOR). Thus tweak results to full text is misleading. For articles, entering from google scholar may circumvent the problem partially. For books, true research now requires search full text (possibly not available or only available in snippet view) in google books for finding the required source and pages, then searching the discovery for the book for electronic access, similar to finding a physical book.
True full text is strongly required.