You're talking about in-book search (TFA is about search across all books), and yes that was indeed once a known technique for extracting whole or nearly whole books.

That's why publishers responded by excluding sections of books from search (it will list the pages but you can't view them), and individual Google accounts became limited in how many extra pages they were ever allowed to see of an individual book beyond the standard preview pages.

But then LibGen, Z-lib, and Anna's Archive became popular and built up their collections...