TL;DR: You should have both due to the explicit breaking of the robots.txt contract by AI companies.

AI generally doesn't obey robots.txt. That file is just notifying scrapers what they shouldn't scrape, but relies on good faith of the scrapers. Many AI companies have explicitly chosen not no to comply with robots.txt, thus breaking the contract, so this is a system that causes those scrapers that are not willing to comply to get stuck in a black hole of junk and waste their time. This is a countermeasure, but not a solution. It's just way less complex than other options that just block these connections, but then make you get pounded with retries. This way the scraper bot gets stuck for a while and doesn't waste as many of your resources blocking them over and over again.