My biggest gripe is the very rearward location of their main support. It leads to a forward tilt/bounce at higher force levels, especially when standing. Seeing his emphasis on the tilt back to move, I think they optimized the rear mass location for as much of the “guts” as possible, which lead them to keep the mount back there too.
That combined with a questionable structure under it leads to the flex that I see as odd at the very least. I do like that they considered some motion with the rubber feet (lateral roll is good IMO), which I see as better than others that aim for ultimate rigidity.