Wow! I'm so happy to see that my hypothesis is gathering steam, and to share with you all what I have gathered so far:
The 1888 Encyclopedia Britannica lists Illicium anisatum as one of the ingredients used to make absinthe. This may seem like maybe a case of mistaken identity considering that Japanese star anise has gone by many other names as well, but in botanical nomenclature the plant that was first described using a particular latin binomial keeps it, even if they meant to describe something else. The first instance of the recorded name accurately describing the plant in question is the one that sticks.
An absinthe ordinaire recipe from 1891 suggests that 50 g star-anise extract be used to make the absinthe, as compared with 30 g wormwood extract and 10 g each fennel and anise extract. Half the recipe was star-anise extract in 51 l 90%alcohol and 49 l water. (Lachenmeier et al. 2006)
According to an article entitled 'Mechanisms of toxicity of food-borne phytotoxins' (2005), Anisatin is a sesquiterpene lactone causeing nausea, vomiting and epileptiform abnormalities. A case in the Netherlands in 2001 resulted in 60 people being poisoned by it when it was inadvertantly mixed into a star anise tea. Other symptoms caused by anisatin include (and I quote) lower heart beat and hallucinations.
Much thujone is lost in the process of making absinthe (drying the herb, macerating, distilling, removal of heads and tails, coloring, etc). Thujone is a monoterpene. Another compound in wormwood, absinthiin, is a sesquiterpene lactone. This one does carry over fairly well, as it is responsible for the bitter taste of absinthe.
If absinthiin can carry over well (being a sesquiterpene lactone), it stands to reason that anisatin should as well. I'm still trying to get a hold of the GC-MS analysis of I. anisatum from a contact at Kew to compare it to some of the GC-MS readouts of some pre-ban absinthes to see if some of the unknown peaks correlate with anisatin, but so far no response. (I'm not sure if that would be an accurate comparison anyway, but I figure it's a place to start.)
Alternatively, if someone wants to intentionally brew a batch of absinthe with Japanese star anise and send a sample over here, I can probably get an analysis done on it to find if anisatin is present in the final product.