I believe the term, when used in the literature, is more to mean "they don't vote in a manner consistent with how a dispassionate observer with access to global information state perceives the path to achieving their interests."

There's quite a lot of literature on the topic, and it's quite fascinating. For example, higher education has a tendency to change people's answers to a variety of survey questions (summary of this and other phenomena in the book https://en.wikipedia.org/wiki/The_Myth_of_the_Rational_Voter).

Voting irrationally is sequitur from "having interests", just not rational self-interests.

Having interests is not mutually exclusive to acting irrationally.

What you're saying is that people voting for the same party for 30 years, regardless of the political program, are satisfying their interests?