I agree it IS misleading to say it's a 762 HP car. But I also think it's misleading to say it is -- to say it delivers the performance of -- just a 463 HP car.
Consider a 762 HP engine which produces 713 lb-ft of torque and has an ideal dead flat torque curve. That engine will actually output 762 HP when it reaches 5252*HP/Torque = 5252*762/713 = 5612 RPM. At lower RPM it outputs less than 762HP, even wide open: for example, only 136 HP at 1000 RPM as the car begins to accelerate. Tesla's motors behave just like that engine until they hit 3409 RPM, which is 29 MPH. At that RPM they produce 463 HP, and above that they are battery limited.
Yes, the argument on the other side is that the motors are also behaving like a 463 HP engine that would produce full power at a more normal 5000 or 6000 RPM with lower torque, but where the car has very short gearing that could lay that full amount of power down on the road at 29MPH. In that case the car would need a large number of quick-shifting gears or a CVT to keep RPMs in the power band as the car accelerated from 29 MPH to much higher speeds. That would be an unusual set-up. My point is that subjectively off the line, the P85D behaves like a 762 HP car with more conventional gearing. After all, at 463 HP the car is dragging around 11 lbs per horsepower. What 11 lb/HP ICE car has such world-beating performance off the line that it can make unwary passengers scream? I think none. Hence my comment that it is ALSO misleading to classify it as merely a 463 HP car.
I should add there is also evidence (see my long write-up) that driveline losses from motor to tires are very low compared to ICE cars with transmissions. So in terms of max HP actually delivered to the pavement, it may be 10 - 15% higher than what a 463 HP ICE car could deliver.
I don't want to sound like an apologist or a fanboy -- and I'm upset at the company for changing the specs on the P85D ludicrous upgrade just after I put down my 500 bucks -- but on the other hand, I really love the feeling of kicking the pedal from a standstill.
The stock ones I have had on the dyno have a drivetrainloss around 18% from the engine to the hubs if the stock engine hp figures are correct. Its also different from dyno to dyno. I use a Dynopack that measure the power on the hubs and not the wheels, so it may be a few more % loss on the wheels. 
