I doubt by much as the factory boys weren't stupid and the failure rate of the bushings would have made it apparent. However that is providing the LCA and Strut remain in a fixed position to each other as designed. When one starts playing with the length of the strut that goes in the sh-tter Bubba's ideas are not always good for the distance and many times lead to other problems. One would have to geometrically lay it out to see exactly how much movement was at the pivot point in the factory design.
I strongly suspect the adjustable struts came into use as other mfr's did use the strut for adjustment BUT with a different LCA design and Bubba couldn't get his caster where he wanted so let's do what them people at Ford and GM did on SOME of their cars. Hey Leroy, go get a couple of cases of beer while I start hacking this idea out. Next thing one sees is they're being marketed as a solution. Remember Slick 50? MPG improvers, engine rebuild pellets for your oil burner? LOL Those and thousands of other products were all designed to get money form your pocket to theirs and some were quite successful LOL

As far as the urethane goes, had them in my 68 Charger for 30 years without an issue. Other cars as well