Soldato
I think the DC2 type R has a lower brace as standard on the rear subframe. Stops the deflection between the two inner mounting points for the lower arms
And the gauge of steel was taken up to 3mm along with the inner wheel housings, there are quite a lot of load paths in that little section thanks to the largish anti rolls bars.
Its minor optimisation rather than anything drastic though but can allow marginally stiffer bushes for the same NVH hit to tighten handling or drive feedback.