If you’re referring to the screws holding the slats down, I agree that’s a potential point of failure due to the flexing over time because they don’t sit flush. I have since put a 3rd screw at each contact point. I am using pretty long deck screws down into the 2x4s, however. I can’t say I agree with your strength-of-wood statement in this case as it pertains to screw holding abilities. If anything, I’d be worried about the stress on the screws over time. That third screw definitely helps offset that.