Who is "they", what testing did they do, and why would they need guidance if they did testing?
Also the car not being set up for dyno testing- the existence of a dyno mode only became public (found hidden in an EPA document) earlier this year.
When the car mags do testing of a car, they typically coordinate the article with the auto manufacturer. Every mag used the 450hp figure so it was probably at the guidance of Tesla. Motortrend has an especially tight relationship with Tesla and they were one of the first with the 450hp description of the Model 3 Performance.
Also, the latest dyno test were done after dyno mode was released.
Tested: Tesla Model 3 Performance And Standard Range Plus Dyno Results
472hp was the result of the Performance model. I'm just trying to reconcile why the big difference.