You said yourself that Eureka has multiple instances so just those people could be split between multiple instances as well.
Just because it's a bot town on a new data center such as Materia doesn't mean it is everywhere else. Old relic grinds have always been a very popular endgame content since "old" existed and that includes the stormblood relics. It's not hard to come across someone saying they are working on an old relic if you are in a lot of game chats.
I've not encountered bots when I've been into any of the 4 areas, just normal people spawning and doing NMs or BA but it will be interesting if I ever run into them. Bots being there doesn't mean players aren't though.