The Gospel alone....I believe He is saying is what Jesus did alone..
Yes, you are correct.
The
Once Saved Always Saved adherents (the majority of them) are stuck on the part of the gospel that speaks to the lost, Believe only and be saved; they fail to grow in the faith resulting in their infant stomachs not capable of digesting the spiritual meat of the gospel:
"Whosoever is born of God doth not commit sin" (1 John 3:9)
This is because the spiritual milk of the word that is supposed to mature them has been poisoned by the traditions of men. And after sometime they read less and less of the Bible and more and more of what their teachers write.
"For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away their ears from the truth, and shall be turned unto fables." (2 Timothy 4:3-4)
We must grow in the faith with the word alone:
"As newborn babes, desire the sincere milk of the word, that ye may grow thereby" (1 Peter 2:2)
"That we henceforth
be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive; But speaking the truth in love, may grow up into him in all things, which is the head, even Christ" (Ephesians 4:14-15)