Oh my gosh I'm terrible with names so I didn't catch that that Siggraph paper and Antimony were from the same person! Both are so neat. You do great work!

Absolutely this. "PII" is a moving target that's heavily context-sensitive. Any entity that's large enough to care about PII almost certainly has some category of it that would be indiscernible from a handful of jumbled alphanumerics without a clear understanding of the context, both linguistic and organizational, in which the text sits. A general-purpose model would struggled to solve this in the broadest case, and will certainly be incapable of solving it in any specific case.