What is “true” about the true vine

Then certain individuals came down from Judea and were teaching the brothers, “Unless you are circumcised according to the custom of Moses, you cannot be saved.” And after Paul and Barnabas had no small dissension and debate with them, Paul and Barnabas and some of the others were appointed to go up to Jerusalem to discuss this question with the apostles and the elders. So they were sent on their way by the church, and as they passed through both Phoenicia and Samaria, they reported the conversion of the Gentiles, and brought great joy to all the believers. When they came to Jerusalem, they were welcomed by the church and the apostles and the elders, and they reported all that God had done with them. But some believers who belonged to the sect of the Pharisees stood up and said, “It is necessary for them to be circumcised and ordered to keep the law of Moses.”

The apostles and the elders met together to consider this matter.

John 15:1-8

”I am the true vine, and my Father is the vinegrower. He removes every branch in me that bears no fruit. Every branch that bears fruit he prunes to make it bear more fruit. You have already been cleansed by the word that I have spoken to you. Abide in me as I abide in you. Just as the branch cannot bear fruit by itself unless it abides in the vine, neither can you unless you abide in me. I am the vine, you are the branches. Those who abide in me and I in them bear much fruit, because apart from me you can do nothing. Whoever does not abide in me is thrown away like a branch and withers; such branches are gathered, thrown into the fire, and burned. If you abide in me, and my words abide in you, ask for whatever you wish, and it will be done for you. My Father is glorified by this, that you bear much fruit and become my disciples.