This is such a dishonest reading of the text that I suspect you didn’t read it at all.
Nobody said that shark attacks don’t happen, just that they are rare and that sharks are incredibly ecologically important. “Sharks can, but almost certainly won’t hurt you” and “sharks are ecologically important” are only statements at odds with each other if your goal is to turn the entire planet into a daycare.
No, this isn’t like immunity that a mother’s breast milk can confer to an infant (which is provided through antibodies). What they found in the milk is live, active virus. Trying to get immunity from that would be like trying to get immunity to HIV by drinking the breast milk of someone who’s HIV+.