I don't know when they started using truss rods, I still have the same TH5 as mentioned in that thread. All the Takamines and Hirades that I have seen have all had truss rods, no one that I know has ever had to adjust them. Our climate here is slightly more humid and is fairly stable. My teacher still has an older one with a truss rod, probably 15-20 years old now.
Hirades are not so widely available now, I understand that one of the major distributors has dropped them from their range.
"When I was younger, I could remember almost everything, whether it happened or not." Mark Twain