I don't know who renders "official" verdicts on these things. The link in the OP has expired, but I believe it suggested that the story was consistent with information from other sources.

Long term survival at sea is not unknown. There is a case on record from WWII of a seaman adrift for 133 days - 50 with lifeboat supplies, but the final 83 with only rainwater and fish. I would just think if you can get by for 83 days, you have achieved some sort of equilibrium and can keep going for much longer. After all what could be healthier than eating lots of fish - omega 3's and all that sort of good stuff...