Was the 80GB actually proven on the 10GB model? I thought it was a mirror of the first 40GB.

According to this paper, yes: https://www.researchgate.net/publication/408132536_A_Canary_...

But I can't see any independent confirmation and having personally tried to contacted the paper author I received no response. So, I'm not sure the paper findings actually hold.

I'm now on the process of investigating this and, if I achieve any conclusive result, either for or against, submit a new paper on the subject.