The devil is in the details.
I am guessing you might be right.
Unless this research is broken down by hospital I would not give it much credence.
Unless blacks and whites are treated differently in THE SAME HOSPITAL it is a bunch of race baiting hog wash.
Where are blacks most likely to go to the ER? In a metropolitan hospital.
What is a metro hospital very likely to see? Drug seeking behaviors.
What happens when ER doctors see a lot of drug seeking behavior? They become cautious about prescribing pain killers.
Everything in human behavior is conditional. If you learn that certain types of people and certain types of behavior are drug seeking types you as a doctor are not going to give a person displaying those behaviors powerful drugs. It is what the law requires.
I read the entire article, and I saw no indication that they studied differences within the same hospital. Therefore, the entire study is worthless.
My take on this is that the authors were too eager to trot out sophisticated data analysis techniques, and did not focus where they should have, the study design.
There is a paradox in (especially) social and medical study data analysis, where no difference can be seen in individual data sets, but when they are combined, apparent (but not real) differences appear. See Simpson’s Paradox.