In dying, the incarnate God paid the sin debt of every human being. There is no confusion at that level.
The confusion sets in from a misunderstanding of what the debt of sin actually is, and what it meant for Christ to pay it.
Sin is acting contrary to the will of God, and that means acting contrary to the will of Love. To sin against someone is to act towards that person in a way other than as Love would act. The other is therefore deprived of what Love would have offered him. And Love itself – that is to say, God – is diminished by the disappearance of the love I have withheld from the other. That is the twofold result of sin: “What you do to others, you do to Me.”
In that way, two spiritual debts are created by every sinful act (Such acts of course may also incur a material, worldly debt, but that isn’t our present topic.) There is a debt incurred towards the other, and a debt incurred towards God.
In both cases, the so-called sin debt is more meaningfully to be understood as a love debt.
The love debts we owe others can only be cancelled by the ones we harmed, and only by a self-sacrificial act of forgiveness. Christ’s death did not pay down those debts.
The death of Christ, that is, the death of the incarnate Son of God, was infinite Love exhausting Itself – and dying – to pay the incalculable love debt of all humankind to God.