We noticed that the SPO Information Management Policy is not taking effect on the custom fields created for list. It seems that it only supports the pre-defined fields, which are not the ones that we want. We followed the steps in “Create a policy for a list, library or folder (location-based retention policy)” in https://support.office.com/en-us/article/create-and-apply-information-management-policies-eb501fe9-2ef6-4150-945a-65a6451ee9e9 and it is not showing our desired results. Please consider supporting the custom fields.