I can see where it clarifies things to show some corrections of leaders so that future generations of the church can be completely sure about what they are being asked to teach. It helps, rather than hurts, to have Peter a bit off track or James a bit off and then corrected.
I don't think James is at fault in the letter (he is just showing that a body has to be active to be alive). But he is named in Gal 2.
I am sure that at a later date James came into a full knowledge of the Gospel and justification by faith.
The book of James is one of the very first books that was written in the New Testament.
There were many that could not turn lose of the law and live by faith.
James also had a problem with uncircumsized Gentiles in Acts 15:1-35.