True the voltage levels at no load have to be the same. But the voltage ratios do not have to be 2:1. As Don and Lloyd say, the smaller transformers are designed with a ratio slightly off of 2:1. That is so at the rated load, with some voltage reduction because of losses in the transformer, the voltage ratio is 2:1.
But it reminds me of the difference between an engineer and a physicist. If a physicist enters a room and sees a naked girl on the other side of the room, he sighs. Because he knows that he can go toward the girl until he gets half way there. And he can half the distance again and again, but doing that will never get him to the girl.
The engineer just barges in, because he knows he can get close enough.
Dan