What that preacher was talking about was that breaking any of the law is breaking all of the law, as far as sin. See James 2:10 and I John 3:4. If those righteous gentiles were Christian, their sins were forgiven. Everyone sins, it’s impossible not to.
If that’s what he meant he should have said so.
Do you think they repented of their sins? Because without repentance there is no forgiveness. At what point do you suppose they resolved not to sin again by lying to the Nazis?