Peanuts, like coconuts, are not nuts. A person with nut allergy is not necessarily allergic to peanuts (and vice versa). They are 2 separate allergies.
Almonds are a stone fruit, too. It's just that the part we eat is inside the pit. Ever notice how almonds still in the shell kinda look like a peach pit?
Peaches and plums used to be cherry sized, too (and cherries are stone fruits as well, but selective breeding got the fruit-to-pit ratio better for peaches/plums/apricots/nectarines).
So some recipes call for processing cherry pits, and the flavor is pretty close to almond extract. Because almond extract is just bitter almonds processed in a similar way.
Yup, my dad is allergic to nuts (hazelnuts, brazil nuts, and walnuts), but has no issues with peanuts. I have a cousin who's allergic to peanuts, and IIRC he can eat nuts just fine.