I agree -- I have a Ph.D. and was a professor who taught Ph.D.s in the sciences and I never thought of Ph.D. "candidate" versus Ph.D. "student" was a big deal. And ABD --
meh. To me, all that means is, "couldn't finish dissertation."
At the school where I got my Ph.D., and the school where I was a professor, you became a candidate after passing prelimis. If you didn't pass prelims, you were booted out of the program. So time and candidacy status was 100% correlated if you were still a student by year 3, and really, the only thing that mattered was getting your Ph.D. or not and how many papers you published. There was no particular reason you would even bother with your masters degree in my field -- I didn't even take the time to put in the paperwork to officially receive my masters degree even though I could have after I acheived candidacy (which involved prelims and writing what was essentially a masters thesis, though we called it something else... I think we called it our "first year project," but the thesis/project was so unimportant in the scheme of things, unless we published it later, that I don't even remember what we called it.).
Anyway, whether he called himself a candidate, a student, or an ABD doesn't really matter to anyone outside of a very small circle of people. Basically, calling oneself a candidate if not a candidate, or calling oneself an ABD, smacks of trying too hard and achieving too little to most people who are in the know.