"Double storey a" refers to the lowercase "a" with a sort of bent-over bit at the top, distinct from the handwritten cursive "a". So you can say it relates to "typography," perhaps, but certainly not that it's limited to "computer" typography.

Early readers — anyone learning the letters for the purpose of reading — will need to recognize the double-storey "a" in order to read books, road signs, or even a smartphone's pop-up keyboard. And certainly to read "The Cat in the Hat" (which is set in Century Schoolbook, according to a quick google).

Sure, we don't (often?) write it like that in cursive, but we read it that way in almost all written material we encounter in our entire lives. You just don't notice because you're used to it — it's the "natural" way for an "a" to look in print.

...Now let's do looptail "g" versus opentail "g"! At least for that one you'll have the smartphone keyboard on the opentail side of the debate (and "The Cat in the Hat" on the correct, looptail side). ;)