Reading 500 pages is a large undertaking. Proficient readers manage ~0.8 pages/minute. That is ~6.5 hours just reading, without any time taken to organize the knowledge. And reading at that speed is extremely hard mental effort, you're pretty much exhausted at the end of it.

Sure, they could be an extremely fast reader and get it done in 5 hours. Still, without deeper comprehension, or organization.

It very much matters to point out that the recommendation is fundamentally self-aggrandizement more than truth.