Ok, I talked in a more depth to my doc since it was just a brief phone conversation before, and here are the takeaways.
The question, to remind everyone, was "have you been told by a treating provider that you have a condition, that if untreated, would be likely to impair your ability to take care of patients in a reasonably safe and competent manner?"
For my doc, the response hinges on the wording of "would be likely." The words "would" and "likely" imply a degree of certainty, which leads him to say "no" in my case. (Compare to "would likely" to "could possibly," the latter casting a wider net.)
Also, he said "impairment" is a big deal, and he is mindful of not using that word lightly, especially in notes about people in high-stakes professions like ours. Could my condition affect my practice? Yes, it could. But impair and affect are by no means the same. A good litmus test is, consider yourself on a bad day - maybe you're at the end of a long call shift, haven't slept, haven't eaten, and just got yelled at by a patient. Chances are your next clinical encounter won't be your best. Compare that to how your health condition affects you, or would affect you if untreated. If it affects you to an extent well beyond the normal variation that comes with everyday demands and stressors, that's an argument in favor of impairment.
Another way to think about it is were I to go off my meds and leave care, would he be concerned about me practicing safely and feel compelled to report me to the board. There are some conditions where he could say with a degree of certainty that things would go very poorly if one goes off their meds, such as Type I diabetes, or Bipolar disorder, or even thyroid disease. But my case isn't one of them.