The problem in my mind with a "clean is clean" litmus test is that it eliminates the word "clean"'s ability to differentiate between sustainable and unsustainable human development.

Using systematic metrics to annoint something as clean so it can get clean energy credits so that people can invest in activities considered cleaner is valuable and useful even if none of the options are 100% perfectly in impactful to the natural world.

OK, but then by that logic, solar and and wind shouldn't be categorized as clean energy either. Clearly it's a matter of degrees and meant as a useful segmentation for taxation, etc.