that study wasn't accurate to begin with. The essential oils weren't tested alone, but rater combined with another carrier oil to dilute them. That substance was dimethylsulfoxide, which is an estrogen receptor agonist. The carrier oil they combined the tea tree and lavender with for the study was a xenoestrogen.
here is a link to the published article regarding that study (look under the subtitle Methods: Mamalian cell culture for the bit about dimethylsulfoxide)
http://www.nejm.org/doi/full/10.1056/NEJMoa064725#t=articleTop
and a quick google search of dimethylsulfoxide (DMSO) will reveal it's estrogenic effects
here is a link to the published article regarding that study (look under the subtitle Methods: Mamalian cell culture for the bit about dimethylsulfoxide)
http://www.nejm.org/doi/full/10.1056/NEJMoa064725#t=articleTop
and a quick google search of dimethylsulfoxide (DMSO) will reveal it's estrogenic effects