Did Old Testament believers have the same in-Christ position as Grace-Age believers?

Les teaches that the Old Testament believer did not have the same kind of position as Grace-Age believers. In the context, Paul was ministering to Gentiles at Antioch, and Jerusalem believers were disturbed that Gentiles were claimed as saved without keeping the law of Judaism. False brethren came in to spy out the liberty believers have in Christ Jesus, seeking to bring them into bondage, meaning back under the law. Les explains that now, when a person becomes a believer of the gospel, they are in Christ. As Grace Age believers, we are in Christ, we are in the body, and Paul and Barnabas were as well. The Jerusalem Jewish believers tried to hang the law on Paul, Barnabas, and the Antioch Gentile believers, but Paul says they gave place by subjection, no, not for an hour; they did not give in.