Many parts from Saleen are not functional either, just like their S281 spoiler. Just for looks, which is cool in it's own way. The problem with the rear shock tower brace is this.
1. Shock tower, like the front strut tower, is supposed to stiffen up the chassis around where the suspension would mount, and keep the chassis rigid under load, so that geometry would not change under flex. Front strut tower brace keeps the towers from flexing inside, and that's a good thing because front geometry for McPherson strut includes shocks and control arms mainly.
2. The rear geometry is calculated through upper and lower control arms. Rear shocks don't carry any load at all, unless you have a coilover setup, which most people on this board don't have. Saleen and KB don't even manufacture Coil-Over setup. So you can sit and re-enforce the rear shock towers until you turn blue, and it will not change anything at all.
3. While Coach Works, and KB at least try to make an honest attempt at making something that might be functional, by making the braces that mount in multiple points, Steeda piece mounds to a soft upper shock mount bushing, and adds pretty much nothing at all to rigidity. Here is a question you gotta ask yourself. Why have reputable suspension builders like Maximum Motorsports, Griggs Racing (AIX fastest car), Global West, or Agent 47 (AI fastest car), who build race car products, have never built one?