You are probably correct and he was wearing the arm restraints.
I would never have felt comfortable driving a modified with nets on each side, the arm restraints are only marginally effective yet better than nothing. I used the advice that Frank Eppolite gave me when I was 15 years old or so, "never let go of the steering wheel when crashing". This works well with dirt modifieds, not so well in cars with rack and pinion steering however. Do not ask how I learned this.