Actually the article you cited does not say that any medical professional believes there are racial differences in sensitivity to pain.
“Racial bias in perceptions of pain (and possibly treatment) does not appear to be borne out of racist attitudes. In other words, it is likely not the result of racist individuals acting in racist ways.”
There appear to be statistical differences in how people of different races are treated for pain. Without doing a full multi-factor model looking at medical condition, gender, age, case load, urban vs suburban vs rural, median income, and other factors, it is hard to know if other factors besides race could explain the phenomenon.