To quote from the article:
"The car's features include aerodynamic wheels with clear plexiglass
covers, and wide side skirts and wheel arches."
To be honest, I can't see them in the pictures either.
Maybe the covers are so optically perfect that they virtually disappear.
More likely, they would have been difficult to photograph due reflections from
their presumably curved surface hiding of distorting the wheel spokes.
Earlier, Frank Lee said they probably weren't mounted for the pix, and he's
probably right.