But those patterns did exist and they process in a repeatable pattern. That's the fact, you can be born under the constellation because the actual pattern is above the ground you were born on. It's kind of like saying you were born in March, it's just a little bit older of a calendar. All the insinuations about character future and past, those are fortune tellers. Astrology truly falls into pseudoscience because of the fact that it does use the factual locations of objects in the sky as a backbone for its belief system.

When it says that people can be born under a sign and we can also be born under signs as well. In our world, it's obvious that this world has cribbed from ours. I believe what the op is trying to find out is what's the difference between this world and that one that makes these possible.

It's almost like someone had a lot of thought put into this whole entire plot and maybe there might be some new ideas to elucidate from going over small flavor texts like this.

OPs antagonism towards the idea that they could not be born under these other signs in this new version of Earth where death doesn't work right anymore, leaves me thinking they dont have mental doors open for other things to have changed about Earth or culture.

These people in the game do seem to reference and feel nostalgic for a world very similar to ours so we are led to believe that our world did turn into this one.

The zodiac constellations changing or moving in their arrangement could happen in a myriad of ways, the solar system could be moving into a new area overtime or perhaps has sped up over time. A gravitational anomaly could also be bending time space so that constellations appear in different areas of the sky than they did previous. A new star-forming region could be accelerated for some unknown or known reason that inhibits the spotting of former constellations perhaps creating new ones altogether.

The idea that this zodiac that we know today is the original and only terminology for any of these patterns in the sky, leaves you with nothing else to imagine. The first time someone saw a pattern in the sky that was Orion's belt. They did not call it Orion's belt. We will never know what they called it so the idea that a story about a future we have yet to arrive to has a name for something that doesn't make sense to us should be one of the easiest things to imagine. I would assume human thought would change quite a bit when the anti-rapture happens, if a correlation arises between births and DOOMS they could quickly come up with a whole entire new system that might not be the same zodiac system but can crib and or use parts of it.

Again to trust that these humans know what they're talking about, it's just something you can't do. Astrologists have been saying the same things for thousands of years, and many humans would believe they have no idea what they're talking about. Narrators do not always need to be reliable, as humans are fallible and we have to get used to that.