ATN, I'd say it's more likely that the manufacturers understandably want to make their machine look as good as possible in the specs, and there would also be defined standards that apply to the certification of aircraft and relate to the types of proving flights and documentation you must produce.
So the hover ceiling would use maximum power, because the helicopter can actually hover under the specified conditions.
You don't necessarily have to be able to hover to take off, just get light enough on the skids or wheels and you can do the old 'cushion creep' - not all that pretty but it works.