So it seems the issue is that people have borrowing agreements that can be recalled early (seems like it functions like a margin call in a way). Call it half-naked shorting, I guess. Still seems risky. I feel like they could've just bought call options and called it a day instead. Maybe that's too naive or call options are hard to find/pricey for Gamestop?
That still doesn't explain how you know folks aren't naked shorting. Maybe you can read the trades?