We have two young cats (10 months old) boy and girl - both neutered and happy, sweet little things.
Ever since they were old enough to go out, which they love, they poop outside. We still have their litter boxes in the same places they've always been, which we keep filled and clean.
They always poop outside. Even overnight they save their poop for their morning look out but they just seem to prefer peeing in their litter boxes. It's not a problem for us but just checking it's normal as it seems a bit weird!