From what the game tells, Seedlings were Nehma's personal agents of chaos. But ever since Nehma got turned into a lawn ornament after Eden's uprising, she was presumably put out of commission for a while. The player Seedling seems to be implied to be the first Seedling she created after a long while and managing to finally recuperate enough strength while being a BBQ stick. And even then, Nehma seems to have only scrounged enough strength to only create one: The player Seedling.
But the thing is, knowledge of Nehma herself and by extension, the Seedlings, doesn't seem to be common knowledge among Nymphs. Which means that the existence of Nehma (and thus the uprising against her) was likely only known to the elite/older Nymphs of the colonies. Eden's uprising against Nehma was likely a coalition by multiple colonies. And Vorg, probably part of the forces that Gypro-Verde (or Gardina, if the split already happened by that time) contributed. Nehma would've obviously used her Seedlings to defend herself and was likely the main enemy force that the coalition fought. And that's why Vorg was aware of them. She likely killed quite a few of them during the fight against Nehma. Hell, said coalition probably went out of their way to exterminate all Seedlings still wandering around Hod in the aftermath.
What I want clarified is how much time passed between Nehma getting hoisted up as a flag and the start of the game. Notable historical events like the fall of Nagara, the Assassination of Queen Gypro-Verde (and the later disillusionment of Vorg with Gardina), etc seems to have only happened after Nehma's "death". All that stuff didn't happen in just an afternoon. The extreme enshittening of Hod began with the flashpoint that is the death of its "God".
And hell, you can even wonder about why the Nymphs decided to kick off Nehma from her throne anyway. Is it really just a case of "We don't like a shadow puppetmaster manipulating everything tyranically behind the scenes because we want muh liberty and freedom (so that we can enforce our own brand of tyranny lmao)". Or did the Nymphs of the colonies have a more personal agenda against her?