The SDA church has been teaching the trinity doctrine since about the 1920s however when Barnhouse and Martin studied SDAism in the 1950s they confronted the scholars of the church with a case of literature with articals all with the church logo but with differing positions such as the one mentioned here trinity v arianism. Of course the leaders were shoched at the revelation but it does represent the SDA church a small number are still Arian.
In the 1950s the SDA book Questions on Doctrine was printed while at the same time the book The truth about SDAs was printed by walter Martin both books were sold in christian bookshops both books were sold extensively to SDAs by the church. The books were as a result of the meetings by walter Martin and scholars of the SDA church.
Some SDAs even today beleive Questions on Doctrine by the SDA church is damable herecy. These are the more cultic members of the church