If you have a 333 Exemption you can see your PIC requirements under Conditions & Limitations (in my exemption it's #13)
Conditions & Limitations:
Under this grant of exemption, a PIC must hold either an airline transport. commercial, private, recreational, or sport pilot certificate. The PIC must also hold a current FAA airman medical certificate or a valid U.S. driver’s license issued by a state, the District of Columbia, Puerto Rico, a territory, a possession, or the Federal government. The PIC must also meet the flight review requirements specified in 14 CFR § 61.56 in an aircraft in which the PIC is rated on his or her pilot certificate.
For clarification the Sport Pilot Airmen certificate is the "least" you can hold in "standard" terms but I have heard of others who have complied with their 333 Exemption by using a Glider or a Balloon rating. But you have to have an Airman's Certificate which include ground school and some amount of "stick time" in the air. If someone is telling you otherwise you need to contact your local FSDO and get that in writing TODAY.
In all fairness at one time it was written that a Private Pilot certificate was the min allowed. That changed to a Sport Pilot certificate so that a UAS operator wouldn't have to get a full blown Airman's Medical certificate and could utilize state issued drivers license instead. By downgrading the requirement to Sport Pilots License made a lot of sense.