The holes either need to be slotted or grossly over-sized to slip onto the studs because they point in to the center of the car at an angle. If they fit "exactly" it would be impossible to get the bar on. Also the slots are designed with the tolerance of different vehicles in mind, as well as what we can predict to be strut tower fatigue in aging vehicles.
With that said, the clamp load for a single stud/nut of that size at around 12ftlbs of torque is in excess of 2000lbs. So you're looking at over 8000lbs total. That bar isn't going anywhere. Just like the stock strut tower to firewall brace doesn't move or you'd be able to see rub marks under it.
It might be even easier to visualize if you think of a camber plate where the entire strut assembly is held by 4 small allen bolts.
I picked the Raceseng Camber plate because I think it's beautiful
You have the weight of a corner, and a lot of force going through it to the strut tower, and they don't slip despite the fact that they are small in size and low torque in a long slot.
Nothing to worry about as far as slippage, the clamping force is HUGE. You can always put it on, then drive the car as aggressively as you can, and then check for signs of slippage (it would be obvious rubbing of the powdercoat) under the head of the nut.
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Engineering