I think the only one who gains the memories of everybody is Stella, who is permanently connected to Punk Records.
My interpretation is that each Satellite is an independent being, and they aren't connected to Punk Records. Once per day, each of them sync with Punk Records by uploading their memories and skimming information to check if there's anything they want to assimilate (kinda like looking at a daily catalog of new itens and choose which ones you want to purchase). However, they can't really have all the info on Punk Records in their own brains, as it's too much for anyone without the Brain Brain Fruit.
Now, why didn't Stella know of York's activities? Maybe Stella has access to all information but needs to search it. However, I feel that doesn't work, because Stella and the other Punks would obviously skim over new uploaded data and one of them should notice York's activities.
So, since they are all geniuses, I think York hacked the sync system and found a way to only upload what she wants. By erasing pieces of her memories that would be sent to Punk Records, she kept those activities away from the other Punks.