It's still a worthwhile comparison because it demonstrates that some people have a desire to turn their death into something meaningful or useful to others. After, all question was "what would motivate someone to willingly transform their last moments into a medical experiment?", and my examples are about motivation.
For some that motivation might be strong enough to be willing to undergo some discomfort (if, indeed there needs to be any discomfort in the first place, which isn't clear). For others, it might not be.
If you say so--for the sake of winning an arguemnt--there you go. You can have your victory, I don't care. The difference is still very fundamental, in a literal sense. Most people opposed to organ donations have religious reasons. I am an (not opted-out) organ donor, and I don't care about that. However, I would violently oppose being subjected to more machines then absolutely necessary while dying.