If it's anything like car and truck manufacturers, they start building the next year model around September of the previous year, so if it was built in December 1969, I would expect it to be called a 1970 model year by the manufacturer. I ordered a 2022 model year truck from the factory in June 2021, and it was built in October 2021 and I took delivery in November 2021 of my 2022 model year truck. If your Honda was built in December 1969 it probably didn't even arrive in this country until 1970, so I don't know why they would call it a 1969 and sell it as a year-old model. So... I would call it a 1970, especially since the K0s are the same between those years anyway.
I just bought a "1970" CT 90 that says 1970 on the title but is really a 1969 K1, not a 1970 K2. When ordering parts, you need to know the "K" number. That's what is important, not the year that is on the title or the manufacturing year that is on the bike.