If you loosen the screws on a bolt on guitar while under tension you will feel the strings pulling the neck out of the pocket. This design is certainly overkill / marketing, as you would want the angled screws to be angled the opposite way to ideally counteract that force.
But if Keefer can smack a man with his Tele and keep playing in tune, four screws is probably all you need. Heck, 70s Fenders had three and Danelectros sometimes had two, and they were fine.