They could offer the cheapest price, but they can’t lock it in. The lender requires documents. The lender will continue to request additional documents, regardless of how many documents you’ve submitted.
The lender will use a trap when they make reasons why you should not be denied their low interest rate. They then proceed to request documents. The lender forces you to conduct the necessary investigation yourself to discover the lowest rate. The lender claims that they were able to offer you the best rate because you did the investigation.
In the event that you deal with a lender, they should have the ability to set an interest rate immediately. If a lender can’t accomplish this, it is best to locate a lender that is not running scams.