What you need to know about the A-2 status
The Secretary of State must accept A-2 applicants. A-2 and A-3 visas are given based on reciprocity 8 U.S.C. §1101(a)(15)(A). Although one may possess an A-Visa, they are not automatically considered a diplomat.
The issuance of an A status is prima facie eligibility under INA §101(a)(15)(A), 8 U.S.C. §1101(a)(15)(A), but it is subject to Secretary of State accepting credentials and one is admitted for duration of the status.