Read closely. They say the car came originally with a 3 speed with overdrive, but now fitted with a proper 4 speed Top Loader. Yes, if to be right for the year, it should have a T10, but I don't think they are worried about originality since the 3 speed has gone.
I did see that it originally was a 3-speed with OD. However, they shouldn't have used the word "proper" when describing the Toploader. They could have just used "now has a _____". The wording used could be a bit misleading since they also claim it's a "numbers matching" car. Personal opinion-they just don't know any better.