Your college chemistry and biology classes must've been extremely elemental for the sheer mention of chemical dependency to urge you back so easily
It's not semantic at all. It's specifically defined on the page I quoted earlier from the University of Texas at Austin's Addiction Science Research and Education Center. You should read it, at the risk of feeling like you're back in college
Welcome to (1) College "research" center and their (2) hypothesis and (3) ambiguity as illustrated in "your" examples:
Ambiguity to support a hypothesis: "science is beginning to learn". Would science be the Austin Research Center or someone else?
Hypothesis and Ambiguity: It appears that a person must have, wait, here comes the empirical scientific term "what it takes" to ... here it comes ... "become dependent on drugs."
"Evolving", meaning still changing, research... according to DSM criteria (that would be selecting a specific set of criteria that supports their hypothesis.)
What we know is people become chemically dependent on drugs, narcotics. Physically and mentally. The notion that only "brain diseased people" get addicted to drugs sounds like a thesis of a dope using med student.
What we do not know, and what the hypothesis (educated guesses) you used to support his notion, is what is unknown and the subject of changing research.