I think it was more that the harm caused in these (presumably) avoidable examples is not counted negatively. Preventing cancer makes less GDP than curing it; smoothly transporting oil without incident makes less GDP than spilling it.
> smoothly transporting oil without incident makes less GDP than spilling it.
Oil creates huge economic activity when used. It does no good spread over the ocean. The cleanup generates activity, but it's clearly far better for GDP to smoothly transport oil around than constantly lose it, if only because ships constantly sinking would cause people to transport things way less and so markets would be less efficient, yielding less wealth.