Without an understanding of what salvation really is, there is no way to understand the relationship of sin, confession, and repentance.
We agree on this. This why soteriology of OSAS creates some major problems regarding sin, confession, repentance, judgment, forgiveness… - and some questions whose only possible answers reveal them, such as here.
We are saved from the power and penalty of sin because God CHOOSES to not count our transgressions against us because we are trusting in His mercy and forgiveness for those sins.
God’s justice was satisfied with the death of Christ on the cross and sin no longer has any dominion over us. We have overcome the world and death.
I am crucified in Christ. IN CHRIST, God counts me as having died to sin and since Christ paid the penalty for that sin, IN CHRIST, that penalty was paid for me.
So sin no longer has any power over me and whether I die with unconfessed sin or not, as I died in Christ, I am alive in Him and His righteousness in credited to my account.
THAT is how I am saved, once for all and that’s why OSAS works.
Greater is He who is in me than he who is in the world. Sin is not greater than God.