Yes, I thought nautical miles per hour per second was a bit of nonsense. Whoever put that graphic together was an idiot.
Indeed, why measure the rotation of the Earth in MPH when NASA and Roscosmos and China use the Metric system for measuring the velocity and acceleration of spacecraft? It’s absurd. Now I myself do not mind people using customary units on Earth, indeed, the aviation industry depends on them, for legacy reasons; it would be extremely difficult to change the aerospace industry outside of the former Soviet Union, which alone used the metric system completely, to get rid of knotts and feet and also another non-SI measurement, the Flight Level, as standards. Indeed, incorrect metrication of aviation and the mixing of the metric system and customary units caused Air Canada’s “Gimli Glider” incident, as well as an embarrassing mistake NASA had with the Mars Climate Orbiter. Fortunately no one was killed in either instance, but as a software engineer I have become extremely wary of using non-standard systems of measurement, whether these are customary or SI, or of changing from one to another, or of situations where one must be converted to the other, due to the propensity for disaster.
By the way, here is a fun fact: the US was one of the first countries to adopt the metric system in the 1860s via treaty, and after doing so redefined all US customary units to be based on metric units, so in a sense US customary units are an abstraction on top of the metric system, unlike their British Imperial equivalents. And for casual use I think this is fine; I really don’t think people should be forced to use systems they are unfamiliar with, for example, when it comes to temperature, and changing our road signage such as speed limits, or those in the UK, to metric, could be very problematic. Actually when it comes to Metrication, your country of Australia and that of New Zealand are ahead of the US, the UK and even Canada, where the railroad industry, for example, uses non-metric units to maximize compatibility with the US railways, because the two Canadian railroads always operated in the US to some extent, for instance, the Grand Trunk Western was owned by the Canadian National, and the SOO Line was closely associated with and later owned by the Canadian Pacific and since deregulation, the CN and CP purchased other major railroads such as the Illinois Central and most recently the Kansas City Southern, which also extends deep into Mexico. Basically, the railroads of Canada, the US and Mexico function as a unified system, with only the Alaska Railroad being isolated from the rest of the network, but it still follows all of the same standards. The narrow gauge railroads in Newfoundland were abandoned, the systems in Central America have disintegrated, except for the former broad gauge Panama Canal Railroad which was converted to standard gauge and operates like the American railroads, and also the Cuban railroads follow the North American style of operation.