If I were an attorney for the plaintiffs I might start by offering as evidence all the articles, written by automotive experts, that described the car as making 691 horsepower (not motor horsepower.) I would then argue that either all of the automotive journalists were confused, as evidenced by the articles they wrote, and their organizations published, or perhaps there was a press release that actually failed to say "motor horsepower" and said "horsepower" instead. If even the automotive experts were confused, it stands to reason that the general public would be as well.
If they were not confused, but there was a Tesla press release that simply said "691 horsepower", that would be even worse.
Either way, the evidence would be pretty compelling.
You're operating under the premise that the magazines "didn't know any better".
The articles which they wrote, do not necessarily indicate, and is not necessarily evidence, that they were "confused".
If the magazines, or those at the magazines, knew better than to go about stating "691 horsepower", but did so anyway in order to sell magazines, well then that's not Tesla's problem.
It's going to be hard for the magazines to contend that they were "duped", if no one at Tesla ever told them that the cars that they were handing over to them to review, had "691 horsepower", but they elected to write that anyway.
Also, it would be easy to prove that the magazines either knew better, or should have known better, than to go about exclaiming that the car had 691 horsepower if they had prior experience reviewing electric vehicles in the past. If they're reviewing such cars, well then they should have been familiar with the standards under which power is measured in them.
Most of the top auto magazines out there, do have some prior experience reviewing EVs.
But lets say for a minute that they were "confused". They should have been savvy enough to
familiarize themselves with a product that they were reviewing.
Especially if they're holding themselves out to the public as being "experts", and holding out their periodical as being trustworthy.
That they didn't know, if that is indeed the case, only proves that they were just as lax, if not more lax, at doing their homework as that small group of consumers was.
And it's even worse and more inexcusable in their case, because they are supposed to be "automotive experts".
As mentioned before, it's going to be hard for the magazines to cry that they were "duped", if no one at Tesla ever told them that the cars that they were handing over to them to review, had "691 horsepower". If there is nothing in any manifest when the car was delivered stating "691 horsepower", and nothing in any paperwork accompanying the car when delivered to the magazine for testing saying "691 horsepower", then that bodes well for Tesla.
Tesla can't be held responsible because your writers and editors didn't get off their duffs before spreading information that Tesla themselves never said or decided to state something which Tesla never stated.
If any evidence can be found of Tesla having made any attempt(s) at correcting the magazine's writers or editors, emails, private correspondence, well then that also works in Tesla's favor.
If it can be shown that the magazine's editors knew or should have known, through prior review of electric vehicles, better than to do what they did, well then again, that bodes well for Tesla.