High precision means resources are missed.
High recall means sifting garbage.
Q: Based on what assumption?
A: No assumption, observed behavior of texts and search engines.
Q: Based on what texts?
A: All texts, yes, all texts.
Q: Texts where same subjects have different works/phrases and same words/phrases mean different subjects?
A: Yes, those texts!
Q: If the subjects were identified in those texts, we could have high precision and high recall?
A: Yes, but not possible, too many texts!
Q: If the authors of new texts were to identify….
A: Sorry, no time, have to search now. Good-bye!