I enjoyed reading this so much. This is, sadly, spot on. It gave me a genuine laugh.
That said, of course, it should still be one's go-to judgment to professionally refuse that particular request. I didn't have specific training for most of the situations that were foisted upon me when I managed a small restaurant (and you literally described my "training" to a tee), but I did know that "go fetch someone of a lighter skin tone" was not ever going to be the best solution.
ETA - Maybe this kind of training will become a thing now. Maybe some restaurateurs will see this incident and enact anti-racism-accommodation policies at their own establishments. I wonder how often things like this happen? I honestly have no idea.
To be honest, for a chain like that, it's probably SOP to have customer management training of some sort. Partly to standardize it, and partly because it's dirt cheap. There are hundreds HR contractors who offer a suite of online 'courses' on a subscription basis. Most major chains I've worked with just make it part of the onboarding process.
Mostly in food services, it's drunks. They get handsy, they get grabby (I learned to always tuck my tie into my shirt so it didn't turn into a leash), they get table-poundy and shouty, glass and plate smashy. Ultimately about half of them get a tour of the parking lot. Whether you have been formally trained on this or not, you don't become a store manager without a few years of experience, and you've had to deal with this every day, so it's not going to be a OMG! situation. At that point in one's career, it's just tedious.
However, racism is not always singled out, since it's only one of so many examples of customer intolerance. As somebody mentioned above, it's usually directed against another customer. They don't want to sit near Jews, Turban Twisters, a war amp with a prosthetic, a guy with an earring, kids from the public school, somebody who ordered pork, could the waiter please make the other party move, no we're not moving we have a window seat, they need to move to accommodate my issues. They don't want their food prepared by Muzzies, go page the owner in on his day off to make my meal special like. I don't like the looks of that negro, can you tell him to leave before I call the cops.
Asking to substitute staff is a bit rarer, but I can't imagine it flustering a manager who's likely already jaded.
And on the topic of 'escalating' - yes and so what. Sometimes the customer is wrong. If they want to look like a lunatic, that's on them. And additionally, my experience is that accommodating is ALSO escalating in that the new bar is set. Next time, they come in expecting the entire staff to be replaced by whites, and the cutlery to not be imported from Chinkland, and the billing software not be made by Jews, and it will not end until you have a pure Aryan Nations supply chain. It's not cheaper to accommodate kooks, it's just easier in the short run.
Incidentally, my wife is in a similar situation: she is an emergency room doc, and every shift, there's a patient who refuses her help and demands a white doctor. My point being that anybody who deals with the mass public will recognize this as a pretty common scenario. The difference in nature and frequency just varies a bit by region and vertical.