Not that this is a big deal or anything but I just wanted to point out that the Last Supper ended in chapter 14.
“but so that the world may know that I love the Father, I do exactly as the Father commanded Me. Get up, let us go from here.”
John 14:31 NASB
Chapters 15-17 Jesus and His 11 faithful apostles are walking to the olive groves in Gethsemane. Chapter 18 they arrive at their destination where Jesus will be betrayed by Judas.
A closer examination of John 15 actually destroys Calvin’s theology. Eternal security contradicts John 15. The Father cuts off every branch IN CHRIST that does not bear fruit. Jesus tells His 11 faithful apostles to remain in Him which according to Calvin’s theology it would be impossible for them to fail to remain in Christ. The implications in John 15 are overwhelmingly against Calvin’s theology.
Here is true Christian teaching.
Specifically, Lord Jesus said "Get up, let us go from here", but John does not record any movement until AFTER John chapter 17 as recorded in John 18:1 "When Jesus had spoken these words, He went forth with His disciples over the ravine of the Kidron, where there was a garden, in which He entered with His disciples".
One must be very cautious to avoid adding to the Word of God.
Specifically, the scripture identifies Matthias and Joseph as two men who accompanied the apostles all the time while Jesus walked in and out among the apostles - which includes John chapters 15 - 17.
The disciples specifically identified Matthias and Joseph as two men who "accompanied us all the time" - see that it is all the time they were with Jesus as described here:
"'Therefore it is necessary that of the men who have accompanied us all the time that the Lord Jesus went in and out among us - beginning with the baptism of John until the day that He was taken up from us - one of these [must] become a witness with us of His resurrection.' So they put forward two men, Joseph called Barsabbas (who was also called Justus), and Matthias." (Acts 1:21-23)
In the room occupied by Jesus' disciples who put forward Matthias and Joseph were Peter and John and James and Andrew, Philip and Thomas, Bartholomew and Matthew, James the son of Alphaeus, and Simon the Zealot, and Judas the son of James (Acts 1:13).
Thus, Matthias and Joseph are at least two more people beyond the twelve who are specifically identified at the supper covered in John chapters 13-17.
One must be very cautious because it is easy for carnal man to try to add to the Scriptue, as you have done with your words "Jesus and His 11 faithful apostles are walking to the olive groves in Gethsemane" trying to limit the audience of John chapters 13-17.
Specifically, Lord Jesus said
2 "Every branch in Me that does not bear fruit, He takes away; and every [branch] that bears fruit, He prunes it so that it may bear more fruit.
3 "You are already clean because of the word which I have spoken to you.
4 "Abide in Me, and I in you. As the branch cannot bear fruit of itself unless it abides in the vine, so neither [can] you unless you abide in Me.
5 "I am the vine, you are the branches; he who abides in Me and I in him, he bears much fruit, for apart from Me you can do nothing."
So, He says "in Me" in verse 2, verse 4, and verse 5.
When Jesus says "he who abides in Me and I in him, he bears much fruit" (John 15:5) is profound.
Jesus did not stop there, He continued with "apart from Me you can do nothing" (John 15:5) which is nature shattering!
One must be very cautious because it is easy for carnal man to try to add to the Word of God, as you have done within the Word of God in this passage, because the Word of God says "Every branch in Me that does not bear fruit, He takes away" (John 15:2), yet Jesus does not say there ARE branches in Him that do not bear fruit - no - instead He says "he who abides in Me and I in him, he bears much fruit" (John 15:5).
Adding to Scripture carries a deadly punishment (Revelation 22:18-19).
There is no level that a person can choose Lord Jesus because He said "you did not choose Me, but I chose you" (John 15:16) - Jesus, being God, did not provide any exception for choosing toward Jesus. Lord Jesus speaks to all believers in all time because He also said "I do not ask on behalf of these alone, but for those also who believe in Me through their word" (John 17:20)! All these words of Jesus are at the same supper! All glory is God's! With man, salvation is impossible (Matthew 19:25-26)! All glory in the salvation of man is God's (John 15:5, Isaiah 42:8)!