That there's still shreds of evidence for transformational improvements to the dreadfully arcane, inefficient, proprietary machines that are currently "the best".

Personally, my favorite is the Deutsch-Josza algorithm which illustrates a task which can be trivially understood, and provides exponential speedup over any classical algorithm that I can fathom to perform the same task.

Consider there was something like a half-century delay between the discovery of the photoelectric effect and the invention of the triode.

What's most striking to me is that these inherently optical phenomena apparently haven't been well-investigated for how they can provide speed-up to graphics processing.

Depends how you measure quantum supremacy. If you measure by seconds of computation, then the claim has been debunked since if you rent the most powerful supercomputer in the world you can match the performance of the experiment.

If you measure by e.g. energy usage then the claim remains, since it would cost orders of magnitude more energy to run the algorithm described in the paper than run Google's experiment.