That's a very interesting explanation! Maybe an extra twist to make it less confusing for the customer would be to include a small card in the first package say

That's a very interesting explanation! Maybe an extra twist to make it less confusing for the customer would be to include a small card in the first package saying "your package is on its way! Thanks for ordering!" Some people would still be annoyed, but it'd be the truth, and it would reduce most suspicion that you'd been sold a box of rocks.