It's a little bit like McCarthy being retroactively proved marginally in the ballpark because the Venona papers uncovered Soviet infiltration.
It's interesting that if this Doerr theory is true, that means Zodiac really did resemble pop cultural conceptions of him and other Zodiac-inspired fictional killers: a geek, interested in nerdy fantasy hobbies once considered the province of social misfits. But then again, the occult-steeped tone of the letters and the ciphers themselves already gave that impression.