They specifically modeled the hub & rim as a shell element and spokes as a beam element. That is exactly how a rear wheel is modeled within the industry. To my knowledge every manufacturer that employs FE analysis into their development cycle uses this model. We lease our excess HPC compute time to contractors doing this exact type of development work. First static load analysis, then normal load analysis.

I'll see if I cant pull up another article that does a better job of explaining the torsional effect on the wheel. I thought the article was crystal clear even though the premise was wheelchair optimization.