It's not about having "proof" or what you find or don't find, it's about historical precedent. If you want to predict box office, history is one of the most important things you can know. And the history of the post-Labor Day weekend is that movies drop hard on it. Always have.
No, The Help is not the exact same type of movie as CRA. But that's only insofar as it's not a romcom. But genre is not the most important thing. What's important is that, like CRA, it was a massive crowdpleaser released on a Wednesday in mid-August to a mid-20's OW, and then it dropped 38% on the post-Labor Day weekend. If you look for August crowdpleasers that are comedies or have a comedic bent, there's Guardians of the Galaxy and We're the Millers, which had fantastic legs in August, then both dropped 39% on the post-LD weekend. The fucking Sixth Sense, which was leggier than even CRA could ever hope to be, dropped 28% on that weekend and that was 19 years ago.
The reason CRA dropped 6% and then 10% in its first couple weekends is because WOM spread quickly and people who didn't immediately see it got interested and went a week or two later. But that never meant they were just gonna keep flocking to it over and over. This isn't Titanic and it was never going to be. This is a Get Out, which had an exceptional hold early on because it took people by surprise, and then had legs that were strong but nothing ridiculous. The fact that CRA already dropped harder on its third (and holiday!) weekend than on its second should have told you something.
You're not taking your crow gladly cause you're still ranting. If you call someone a dolt and go "cocaine's a helluva drug" and then a week later they're totally right and you're wrong, you better be able to understand why they were right without them wasting 30 minutes to type it out like I'm doing right now for some reason. You're on a box office forum. Don't go around trashing strangers' box office predictions like an arrogant jerk unless you actually know what you're talking about.