I think you are correct in being discomfited by this teaching. Salvation is the work of God, effected through the death, burial and resurrection of Christ who paid for our sins on the cross. Today, that salvation which Christ effected for us is available to us if we will believe on Him, put our trust completely in Him. Salvation is by faith - period. Not by works, not by secret knowledge or anything else. It is a relationship between God and man, that starts with sincere faith that changes us into a new person. People have been burnt on the stake, ex-communicated, put into prison and through all kinds of difficulties in the defense of this doctrine of salvation by faith alone - it is a precious resource that we need to safeguard.
Ephesians 2:8,9 - For it is by grace you have been saved, through faith–and this is not from yourselves, it is the gift of God-- not by works, so that no one can boast. (NIV)
John 3:15-17 - Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, that everyone who believes may have eternal life in him." For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him.For God did not send his Son into the world to condemn the world, but to save the world through him. (NIV)
Romans 10:9,10 - …because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. (ESV)
This is suspiciously similar to a heresy common in the first and second century AD called gnosticism, where one of the requirements for salvation was a ‘deep knowledge’ and ‘knowledge of secrets’ apart from faith. Paul was very clearly against this in his epistles.
1 Timothy 6:20,21 - Timothy, guard what has been entrusted to your care. Turn away from godless chatter and the opposing ideas of what is falsely called knowledge (gnosis), which some have professed and in so doing have departed from the faith. Grace be with you all.
Paul was very clear that the only knowledge we must have is that of knowing Christ personally since in Him, we have everything we need for salvation and life eternal.
Colossians 2:2-4 - so that they may have the full riches of complete understanding, in order that they may know the mystery of God, namely, Christ, in whom are hidden all the treasures of wisdom and knowledge. I tell you this so that no one may deceive you by fine-sounding arguments.
John 17:3 - Now this is eternal life: that they know you, the only true God, and Jesus Christ, whom you have sent.
In short, knowing Christ is eternal life, believing in Him is salvation. There is no mention anywhere that a full understanding of all of Christ’s teachings or parables is necessary.
To be frank, how many of us can honestly claim that we have understood fully every aspect of the parables of Christ. I don’t think any one in history can honestly say that. I learn more each time I read and meditate on Christ’s words and His parables.
Yes, Jesus did explain the parables in greater detail to his disciples in private, but did they understand it fully? From what I gather from scripture, even the disciples did not fully comprehend the teachings of Christ, and it was a process of gradual and progressive learning even for them - especially Peter! Perfect understanding will come only when we are made perfect and complete, which is something I look forward to on the other side of the river. Right now, I am completely dependent on Christ my Lord for my salvation.
When I sit at the feet of Christ today in prayer and reading of the Bible, He reveals truths from scripture through the work of the Holy Spirit who lives within every disciple - yes, Christ still continues to reveal secrets to His disciples, who became His disciples through faith.