You have assigned code list restriction rule and default value assignment is not working as expected.
Reproducing the Issue
Go to the Sales Work Center as an example.
Click on Sales Quote and Open any Quote.
Click on Products facet.
Under products, in table (list), default value for a field is not working as per configuration.
Code list restriction functionality for a default value will work in Quick create and List modifications (Add row) provided it is for new instance.
And both control and code to restrict field must be present in the Quick create / Add List modification screen.
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