It depends on WHERE he is flying. If it's in CONTROLLED airspace any flight that does not have an FAA Approval is illegal. An approval could be via LAANC or the FAA Drone Zone depending on the area and the specifics of the flight requirements.
DJI Clearance has NOTHING to do with the Legality of flying your aircraft what so ever. If he is using Airmap he could be requesting Airspace Authorizations via that app but B4UFLY is not for that.
From the B4UFLY page:
"The app provides situational awareness to recreational flyers and other drone users. It does not allow users to obtain airspace authorizations to fly in controlled airspace, which are only available through the
FAA's Low Altitude Authorization and Notification Capability (LAANC)."44
For more information about LAANC you can go to:
www.faa.gov