Yeah point taken on a rear drive car.
My AE82 Seca has one. If i'm feeling keen, i'll either seam weld or weld in a 4-point (or, if i can legally a 6-point) cage to stiffen the body and chassis of my ke55.
But where, or how, did you mount the brace ? Where the shockies bolt to the body of the car or where the struts mount to the car ?
A ke70 uses a live axle with a four point linkage and panhard bar system to locate the suspension and shockies and springs to support the axle (or body on the axle. Depends on which way you want to look at unsprung and sprung mass).
Whereas, say, a silva s15, is IRS which uses struts and links to both locate and support the rear suspension to the body.
A car with struts (from a performance side) needs a strut brace between the towers to stop or reduce camber and or toe (and maybe castor) changes during cornering and uneven road surfaces.
Whereas, a live axle car doesn't have to put up with this extra loadings on the suspension pick up points.