Understanding as taught, he was born with original sin but he committed no sin. So I’m a little bit confused by the question, so when they say sinless does that mean he committed no sin or that he did it even have Original Sin?
He did not have original sin, as was also the case with Mary. Unfortunately I cannot remember the sequence of events sufficiently to explain it but it was necessary for Mary to also not have original sin, as the woman who carried Christ in her womb.
Original sin came.from our father Adam, not mother Eve. Eve was tricked, Adam made a conscious choice. Because Jesus’s father was not Adam but the Lord, he was not born with original sin. He was the Son of God, but also the second Adam