Makes sense, think about it.
Would you go to the expense of replacing the whole top, or just use the car for a vinyl top optioned car?
Remember their only motive when making these cars was profit, pure and simple.
It just reminds you how things were really done at the factory back then. When people like those on this forum restore an e-body, the quality control/functionality testing etc is way over the factory bar. Just look at some of the pics of under body prep, Topcat, Farmboy, comes to mind, then the fit and paint, theres Dutch s Cuda, Burdars Challenger, and on and on. The list of cars on this site that are better now than original factory condition is a very long list.