This operation is not supported by directory buckets.
See https://www.paws-r-sdk.com/docs/s3control_get_multi_region_access_point_policy/ for full documentation.
s3control_get_multi_region_access_point_policy(AccountId, Name)
[required] The Amazon Web Services account ID for the owner of the Multi-Region Access Point.
[required] Specifies the Multi-Region Access Point. The name of the Multi-Region Access Point is different from the alias. For more information about the distinction between the name and the alias of an Multi-Region Access Point, see Rules for naming Amazon S3 Multi-Region Access Points in the Amazon S3 User Guide.