The only way to find out it to talk to somebody who worked on the show.
Credits can be VERY misleading. I worked on a show with a "sound designer" credited who literally did nothing on the show. Other films I have worked on people credited as FX editors did design work. The line between the two is blurry to begin with.
I'll bet you a dollar that on this one there was a person responsible for weapons, perhaps another responsible for vehicles, maybe another for aircraft, another for atmosphere and ambiances, another maybe did whooshy special fx kinda stuff with Paul overseeing everything.
I could be completely wrong. There could of been one main guy creating sounds with other people cutting his stuff. But This one had a lot of stuff going on.I seriously doubt that there was one guy responsible for everything in this big beautiful film.
A lot of big shows will have the supervisor assigning different areas of the sound to different people depending on their strengths.