For many, the conventional wisdom is that if the data has successfully moved from a legacy environment to the target system without failure then the migration is a success.
A lot of suppliers will word their contracts to that effect. They will basically state that their role is to move the data and any defects within the data that were not caused by their transformation process falls under ‘buyer beware’ and it’s the responsibility of the customer to fix.
The problem of course is that the customer isn’t equipped to fix the data. That’s why they asked for supplier support in the first place! Because the customer lacks maturity in data quality and data governance they also have no idea of the scale of poor quality in the legacy data.