Direct Answer
The speaker’s claim assumes Paul was reading and thinking in the categories of the Greek Old Testament, where “hamartia” can mean “sin offering,” so 2 Corinthians 5:21 is about Christ becoming an offering for sin rather than Christ becoming morally sinful or a legal container of guilt. It would shift how you read the verse away from a strict “imputation/penal” framework, while still keeping a real substitution and cleansing from sin.