The biggest flaw is psychological. A list of 10,000 items is intimidating. For a beginner or intermediate learner, this book is useless because it offers no pathway to memorization. It is a reference book, not a textbook. You cannot read it cover-to-cover and expect to retain the information.
In regions like South Asia, massive PDF banks of idioms are staple study materials for competitive exams. 10000 idioms and phrases pdf