This comment is the perfect example of why the FDA needs to be involved with this. They gave you very important medical information. Did they a) make sure the information was accurate and b) explain it to you in a way that's understandable to a layperson?
I can easily see a layperson reading that, and thinking "warfarin sensitivity"? As in "food sensitivity", meaning "this is something that isn't good for me, and I should avoid it?" Wait, isn't that the stuff that gave my grandmother a stroke? Holy shit, they killed my grandmother by giving her too much of a medicine that she's sensitive to!"
All warfarin sensitivity actually means, though, as far as I understand it, is that you're likely to need a lower dose than the average patient. If your grandmother had a stroke, it's unlikely that she was overdosed, though - in fact, it's quite likely that she received too low a dose.
If someone has a stroke under warfarin treatment, there are two likely causes: Either their warfarin dose was too low, or they had an artery-to-artery embolic stroke instead of the cardioembolic stroke the warfarin was supposed to prevent. (There are of course other, more rare cases of stroke, but those are the two big ones.)
Do you see how there's a huge potential for misunderstandings here? I'm not saying you suffered this particular misunderstanding, or that laypeople should be stopped from getting this information. I'm just saying, if you're going to put something like that out there and claim it's a diagnostic tool, it needs to be accurate and it needs to be explained, and that's where the FDA needs to come in.