That is an interesting take. Coke ravaged Bowie’s voice. His singing in the 70s is different from the 80s which is also very different from his voice at the end of his life. But like Cash and other, he understood that and wrote his songs differently. I cannot imagine Bowie of 2013 going on tour (even if he was healthy enough) and belting out Changes or Heroes.
Leonard Cohen and Scott Walker that understood their voice were completely different from their younger days and actually changed how they wrote their songs.