One reason to include a count under the Administrative Procedure Act (APA) in your mandamus complaint is to avoid the government successfully asserting that there is an adequate alternative remedy for the immigrant plaintiff besides a writ of mandamus. Another less frequently mentioned reason is to prevent the argument that an administrative appeal must be completed before filing.
In Darby v. Cisneros, the Supreme Court determined that when an agency action becomes “final” under APA §704, courts cannot enforce additional exhaustion prerequisites before allowing judicial review. Although federal courts have the discretion to limit the scope and timing of judicial review when appropriate, APA §704 explicitly restricts the application of the exhaustion of administrative remedies doctrine to situations where the statute or rule explicitly requires it. Courts cannot impose an exhaustion requirement as a rule of judicial administration when the agency action has already reached “final” status under §704.
Since Darby is applicable to APA claims, a mandamus claim submitted without an APA count might not receive the protections provided by Darby, leaving the case susceptible to arguments based on the exhaustion of remedies.