Has anyone ever tried this? What do you think?
Preserved strawberries
No, I haven't. And if I did, I would eat them within a week.
His science is off in a few aspects: first, it's not the raisins, primarily, that do the preserving - it's the sugar, both the granulated sugar and the sugar in the raisins, pulling the water out of the fruit and combining it with the sugar to create a syrup that *may* prevent pathogens from multiplying enough to make people sick. That's a 5:1 ratio of sugar to strawberries.
Second, it's likely that the acidity of strawberries from centuries ago was much higher than the strawberries we have now; a high-acid environment also prevents pathogen growth.
Third, epidiomology was not a thing back then, and neither was the germ theory of disease - no one was keeping track of food poisoning, and people didn't know what caused dysentery, a primary cause of death from extreme dehydration.
There's a reason why it's only recommended to use recipes that have been tested by universities and proven to be safe.