Can you quote that about the Short-Time Levels occupying a plane of existence separate from the things in the Tower, so we know they're not interconnected?
If this were stated directly in a single quote, I probably would. I'm tired of repeating myself.
I think the key point is this: the structure known as the Dark Tower has beams that span across all universes and hold them together—like a kind of cosmic extension cord. These beam-like constructs are what enable the universes to remain in existence. In this context, the phrase 'connected floors' in the sentence can be understood as a metaphor—not for the physical interweaving of universes, but for their being held together and linked through these beams.
The six Beams are like invisible high tension wires that cross at the nexus of the DARK TOWER and hold the Dark Tower in place. They maintain the integrity of time, space, size, and dimension. The Beams can be sensed by those who stand along their paths. Each end of a Beam is anchored by a Portal. There are twelve Portals, each of which is overseen by an animal GUARDIAN.
The Dark Tower is the linchpin of the time-space continuum. It sits in a field of red roses in the fey realm of END-WORLD, and is supported by the magnetic BEAMS which maintain the alignment of time, space, size, and dimension.
The phrase 'connected floors of the same building' mentioned in the sentence is a metaphor that was made more comprehensible in the context of the hospital building where Lachesis and Clotho are located, since beings living on lower planes cannot perceive the higher levels. Even the Tower referred to here may not necessarily be the Dark Tower that connects the universes—it could still be talking about the hospital building they’re in. On the other hand, even if the Tower mentioned here is indeed the Dark Tower we’re familiar with, there is sufficient evidence suggesting that the universes revolve around it (around it, not within it):
A human one! It had to have been so, for know you that true demons, those left on the shore of these worlds which spin around the Tower when the Prim receded, are sterile.
The Dark Tower exists at the heart of End-World. Connecting this universe to countless others, it is the linchpin of the time-space continuum and the hub of the universe the central, stable pillar around which all worlds spin.
This definition of 'connected floors of the same building' is also consistent with the unifying nature of the Dark Tower. In other words, these 'connected floors' align more with the clusters of universes held together by the Dark Tower, rather than representing a quantitative structure:
It's a place outside of time, outside of reality. I know you understand a little about the function of the Dark Tower; you understand its unifying purpose.
And there are texts in which the place where the Dark Tower exists is outside of reality, in a realm where the laws of space and time do not apply.
The Dark Tower exists at the heart of End-World.
[End-World] exists in a pocket where the normal rules of time and space have no hold.
If the universes and the Dark Tower were truly intertwined structures, then Roland’s central goal of reaching the Tower—the very foundation of the entire Dark Tower series—would lose its meaning. The concept of 'reaching the Tower' assumes that it exists outside of, separate from, and at the center of all universes. If the Tower were already present within every universe, Roland’s journey toward it would lack both physical and metaphysical significance, rendering his quest meaningless.
Conclusion: The reason the universes are bound to the Tower stems not from their quantity, but from the Tower’s nature of encompassing and holding everything together—even though it’s unclear whether the Tower mentioned here refers to a hospital building or the Dark Tower as we know it. Moreover, the sentence does not state that these levels exist within the Tower, but rather that they are connected to it, which aligns with the Tower’s unifying nature.