Yes, I have heard of duty of care.
But I don't think it applies to a case like this, where the operator has laid down specific limits, and only allows landings that are permitted under those requirements. They are not subsequently liable if some wombat goes outside those limits either through ignorance or by choice.
If it did apply, then somebody who has built a trolley for their R22 would have to make it big enough for a Mil-26 in case it decided to land there.
Similarly Parramatta Road doesn't have to allow for jumbos to land on it, or for coal trains to rumble through Broadway.