Right, that's what I'm saying. For whatever reason it seems publishers decided they don't want their preview-only books as part of the full-text search across all books. If they decide that, Google has to comply.

This isn't like web search where web pages are publicly available and so Google can return search results across whatever it wants. For books, it relies on publisher cooperation to both supply book contents for indexing under license and give permissions for preview. If publishers say to turn off search, Google turns off search.