Did the various Oneness organizations use "The Four Spiritual Laws" tracts, back in the day? They were big in the AG for a while. I'm guessing not, since they purport to tell you how to be saved, but there's nothing in them about baptism or tongues.
So, why did AG churches get on that bandwagon? I think it was that it seemed like a neat, logical (in AG minds

) presentation that they could more or less agree with. They were OK with omitting tongues and baptism, as the AG doesn't teach that these are requirement to be saved, but rather extra "bonuses" that would come later. Salvation was step 1, water baptism was pretty much mandatory, and tongues was something to strive for and get high-fived (figuratively or literally) when you get it -- especially if you had to work at it for a long, long time, as some did.