The Greek word for confess is homologeo which means to acknowledge, concede or agree with.
From ‘Radical Truth on Forgiveness’ by Paul Ellis
Do you see what I’m seeing though? When you confess your sins - you aren’t telling God anything he doesn’t already know, you’re just agreeing and acknowledging that what you’ve done is wrong. Kind of changes how hard it is to confess your sins sometimes - doesn’t it? If you knew the person already knew - wouldn’t it make it easier to discuss? Once more, if you knew they already had forgiven you - wouldn’t it make it easier to move on and do better?