As bad as Merriam-Webster is, you might notice that 'characterised by habitual and unthinking behaviour' is the fourth, i.e., least common, definition offered, not the first.
Merriam-Webster uses historical order, not how common the meanings are [0], which makes more sense to me - I'm not entirely sure I've ever heard the "reflective" meaning for "reflexive". The "unthinking" meaning is definitely more common.
Words are fun, especially etymology! And students do respond well to enthusiasm for them, or at least appreciate it later. Thank you for that. My wife also teaches English and a foreign language so that’s a part of our life.
That said, how could you have read this and not understood the context for the definition used?! “The phrase “reflexive AI usage” is what triggered my strongest reaction. “Reflexive” suggests unthinking, automatic reliance.”
I thought it was fine to object that you liked the primary definition the most and had the strongest association with it.