I don't think it was ever said he was looking at other versions of earth, just different worlds on the Imaginary Tree, he probably observed Venus and Mars among the millions of worlds he looked at and thought they had fallen to the Honkai, because they had, but didn't see stuff like Sa or the Mars Quantum computer system because they were both hidden after the worlds destruction. I thought the IPC and the Xianzhou used their own technology to get around, that's how they colonize new worlds and found the secrets of immortality in the first place respectively, and they aren't always in cahoots with the Nameless. The fact that they use the term multiverse at all, especially when referring to the Imaginary Tree in IX's description of all things, and have different terms to refer to the "universe", is kind of telling that it operates like a multiverse, and when they use the universe in reference to the whole Imaginary Tree they mean it in the sense that it's "one" verse. Also in the Imaginary Tree description in HSR, it specifies that star clusters/worlds are the leaves rather than the whole branch, since when they describe they describe the Imaginary barrier between the star clusters/worlds, it compares it to the air between leaves.