Former process engineer in an aluminum factory. Aluminum foil is only shiny on one side and duller on the other for process reasons, not for any "turn this part towards baking, etc" reasons.
It's just easier to double it on itself and machine it to double thickness than it is to hit single thickness precision, especially given how much more tensile strength it gives it.
Also, our QA lab did all kinds of tests on it to settle arguments. The amount of heat reflected/absorbed between the two sides is trivially small. But if you like one side better you should wrap it that way, for sure!