I think there's a difference between choosing one more year even though you have your plan in place, and choosing one more year because situations change. In my case, my sabbatical got pushed back a year, and I got an administrative responsibility that reduces my teaching load (and I can "bank" those reductions until I need them). So my new plan is that I'm going to "work" two years longer than my ER plan, but I'll only have to teach for one semester out of that time. Now I have to work on reorganizing the rest of my life to optimize those two years.
Yes, this is different than the stereotypical OMY situation where the person is doing it "just" to increase their cushion or, more sadly even, just to "stay busy."
