How are they " ... strange"? Nothing seems any different than any other vehicle where some vendors post questionable dyno claims and others post none at all.
For example, a larger intercooler won't necessarily give you better dyno results, but it will make your intake air temps more consistent, help with gas mileage while towing, and decrease the amount of spark and boost retard. Only if the existing intercooler was massively restrictive would there be any appreciable gains.
For a stock, non-tuned ST, the ecu is the ultimate arbiter of how much torque (and therefore HP) the engine will make. An exhaust won't make any difference, an intake won't make any difference, downpipes won't make any difference. Why? Because none of those are impediments on this vehicle at the stock HP levels. In fact, as I've posted countless times before, a completely stock ST with just a tune on 93 octane gas can add nearly 100HP.
This is documented and proven. One should be extremely skeptical of any vendor showing results on a stock vehicle of HP or (especially) gas mileage increases.
Now, if you're planning on going beyond those numbers, then you will need other mods to get there.