No, I think you were saying that with the sheer amount of variants on the trilliard scale, the worlds themselves would not be altogether different, simply because there is a limited amount of details that can make a world "noticeably" different from another. However, any world of any given size is still drawn from a mere 4 billion variants, not the multi-trilliard total figure I posted, not because they are the only "different" ones, just because the seed itself provides for 4.3 billion variants, and everything else is size settings.
If you think "what defines unique", then look. If a world is a flat plain, it can be different from another world that is a flat plain if it has a river running across it. Another world may have two rivers. Another may have a round lake in the center. Another may have the lake flat against the world's edge. One may have a volcano. Another may be littered with volcanoes. One may have a volcano inside a lake.
There are countless variants that can make even a set of flat worlds unique. Factor in forests, mountains, elevation changes, temperature effects creating glaciers and deserts, good/evil biome alignment, even stone layer placement, and all these details will overwhelm the 4.3 billion figure. In the end, each world will have enough of the "little details" to be noticeably different, though with the way the randomizer works, there are bound to be a few worlds that differ by a few mountain tiles.