I wouldn't let a pressure washer anywhere near my car. At least you were able to see an instant result of the damage inflicted. Had the tyre suffered damage, you might not have been aware until a high-speed blowout occured. Check out this TyreSafe link:
Under pressure - Pressure washers can damage your tyres - News & Events - TyreSafe
Pressure washers are also very effective removers of wheel and body lacquer.