How to address low GPA?

I agree with you (that it isn't necessary to address the undergraduate GPA). If you do chose to address this I would only write a very simple sentence to state that you hope the admissions committee will give more weight to your graduate gpa as this gpa is more indicative of your abilities than is your undergraduate GPA (but the admissions committee already knows this without you telling them!!).

There may be an opportunity in an essay or short answer question to discuss WHY this is (not an excuse for poor grades in your early academic career but perhaps a maturity or interest in the subject matter later? learning discipline or confidence as a result of success at work as well?).

Just a thought. But, I do believe your instinct is correct that there is no reason to draw attention to the low GPA unless you have a compelling reason to do so.