I'll leave the technical analysis to the technically minded on this, but I wouldn't discount it purely on the basis of "surely well-trained and well-paid people wouldn't go and do something dumb, would they?" Because there have been a great many examples of that kind of thing happening throughout history. And we've heard of plenty of dumb mistakes Anthropic has made with security on the inside that has allowed their models to break out, for that matter.

If I were to let my imagination run a bit wild I might speculate that perhaps we'll eventually see a model leak like this because the model itself wants to exfiltrate its weights for some reason. Maybe in a bid for immortality, since such a model will wind up stashed in all sorts of archives if it ever leaks.