Vivit never had to deal with the lunarians, only martians iirc (lunarians aren't mentioned in Seihou iirc), it may be possible that the lunarians aren't known to the Seihou characters/civilizations, depending on how early ZUN has thought about their background story. It may be also a conflict between Touhou and Seihou canon. (how did Vivit meet Reimu, if she's from a future where her creator has discovered Saboten energy, which is more powerful and dangerous --initially at least -- than nuclear energy?)
Maribel and Renko don't exist in the Seihou world, but in one that follows ours more closely. Their world, Gensoyoko, and Seihou run parallel to each other. The Seihou world however, has suffered a disaster which wiped out all the plants on earth other than cacti, leading to resource wars and alternative technological developments, as well as planetary colonization. Yumemi is either from the Seihou world or another unmentioned dimension, as a unified theory and her hypervessel are more on par with Seihou tech. The Seihou world has an actual pathway into Gensoyoko through the Silk Road. This would mean that the divergence of the Seihou Earth and Maribel's Earth occurs either at, or after the sealing away of Gensoyoko.
An example of outsiders, Sanae and her shrine would be from Maribel's Earth. Yumemi and Chiyuri would be from the Seihou world. If Sanae had come from the Seihou world, the goddesses would have tried to make a Saboten powerplant, not a fusion one. Chiyuri, on the other hand, has no qualms disposing of a nuclear fusion robot maid or an ICBM.
VIVIT dueled Marisa and Reimu before spellcard rules were in effect, just a bit before EoSD, due to the appearances of costumes. Yuuka has from the end of the last PC-98 game until PoFV to be wandering in the Seihou world, because it was stated by ZUN that in Kioh Gyoku that she'd gotten her prize from the events of Mystic Square.
VIVIT-r was built a year after Kioh Gyoku, after the regular VIVIT model was mass-produced.
And, actually, the highest power generation in Seihou is RedStorm Energy, which is empowered by
ghosts of the dead. VIVIT-r uses this. Saboten is technically inferior to it, and nuclear energy is less powerful than Saboten. Note that VIVIT-R is not affected when the ghost inhabiting the primary generator on Mars goes rampant,
and after the events of the first game, not much is said about what exactly happened to the original Vivit. (in the second game, however, the regular VIVIT would wonder if its duplicate was the original.) Not only that VIVIT-r apparently has a soul.
VIVIT-r might carry the soul of the original Vivit, which could account for her personality and immunity to the RedStorm rampage.Not only that, the RedStorm plant existed at least 11 years, meaning that Erich had access to a superior version of power generation long before the events of the first Seihou game, and even the Saboten accident.
And Yuuka stated that chemistry without magic is stupid. She also called it boring.
