I did not say that with the viewpoint I had shared; It says the opposite - once truly converted you can be disciplined here on earth and/or you lose rewards at the Judgement Seat of Christ, but not with loss of salvation. Hebrews has various warnings to true believers; these warnings have teeth.
Do you disagree with Hebrews 12:4-13? How would He discipline us - would it be limited in it’s forms?
Why did Paul say this to Corinthians? Paul says they also are on milk like those in Hebrews 5:12
“Brothers and sisters, I could not address you as people who live by the Spirit but as people who are still worldly—mere infants in Christ. I gave you milk, not solid food, for you were not yet ready for it. Indeed, you are still not ready.”
1 Corinthians 3:1-2 NIV
“He will also keep you firm to the end, so that you will be blameless on the day of our Lord Jesus Christ.”
1 Corinthians 1:8 NIV
“That is why many among you are weak and sick, and a number of you have fallen asleep. But if we were more discerning with regard to ourselves, we would not come under such judgment.”
1 Corinthians 11:30-31 NIV
https://www.bible.com/111/1co.11.30-31.niv