Yeah, when I saw the original comment I tried to find the source of the term but wasn't able to find it.

To me it sounds like medical genetics terminology (known for terms like "penetrance", "allele", "epistasis", "locus") whereas I'm a molecular biologist/biophysicist, which has far more precise ways of describing the underlying physical model.

A term can be still used in literature for historical reasons. Both concepts are not mutually exclusive.