I don't know the answer to this specific question, but:
I see no point in taking any risk by feeding something that is available only once. Imho a risk (although I doubt a real one, it's not harmful to humans and rabbits can cope with a lot more of what botany throws at them) for no real benefit. If it were something you could put on his diet, well, that would be worth a try then.
Same dilemma as getting stranded on an island with unknown plants - no point in trying some random berries if there aren't enough to have actual nutrational value.