Here is everything you need to know about Shirley - seriously
I would suggest to take this audio with a big grain of salt. They have largely missed the main purpose of these negs, at least in my lab experience, from roughly mid-1970s.
I have no idea what the so-called Shirley "card" is, unless that is used in reference to an actual print. I do recall a time when one could buy a so-called "Normal" negative, along with a "proper" print of that negative. Perhaps that's what the narrator, or whomever, meant as a "card."
Regarding the "Normal" reference, I think that this is being mistakenly interpreted to suggest that it means a Caucasian female is "normal," (and anyone else is not, I guess). The reality is that the film "exposure" can be seen as either "correct," or underexposed, or overexposed to some extent. Except that in the Kodak lingo, a "correct" exposure is referred to as "Normal."
Anyone who did serious lab work in a commercial setting, prior to serious scanners, had to set up their printers for each film type by running a set of "printer setup negatives." (These were typically 5 negatives, ranging from 2 f-stops underexposed to 2 f-stops overexposed, including one "normal" exposure.) The main purpose of these was to set up something known as "printer slope." Primarily "slope" corrected for reciprocity failure in the paper as printing exposure times vary.
In truth, printer setup negatives could have probably just been a photo of a gray card, but this doesn't lend itself to visual appraisal of the print. A full-range scene, with skin tones and some strong colors works well for this. This also served as a practical exposure reference for professional photographers who would sometimes ask the lab, how are my exposures?
I have never known of a case where the printer setup negs are used to establish a color reference for the lab. Perhaps this was done in the 1950s or 1960s? As I said, my lab experience didn't start until mid-1970s. The outfit where I worked did a very considerable volume, and at one time, owned three pro labs as well as the largest chain of of one-hour labs in the US.