Why lean for all four???

The Talmud points out the following contradiction:

With regard to wine, it was stated in the name of Rav Naḥman that wine requires reclining.

It was ALSO stated in the name of Rav Nahman that wine does NOT require leaning. How could he have so blatantly contradicted himself???

The Talmud answers - It is not in fact a contradiction. In one statement, he was referring to the first two cups of wine. And in the other statement, he was referring to the second two cups of wine!

But which statement of his referred to which pair?

Some explained it this way: The first two cups of the meal require leaning. For once we begin the seder by celebrating our freedom, you do not have to keep on demonstrating this over and over. You've already done it!

And some explained it another way: The opposite is true! It is the second two cups which require leaning! For that is the moment, at the end of the seder, where we have actually achieved freedom. Whereas for the first two, we are not yet free, but still slaves, so it would not yet make sense to celebrate and demonstrate our freedom by leaning!

And now that one has said it this way and one has said it that way, we now say that both the first AND the second pairs (i.e., all four!) require leaning, in order to satisfy both requirements.