Frogman, it's delight to have you on this thread, not only are you a jazz aficionado, but you're a musician as well. Although I never thought about West Coast from a musical perspective (the softer tone) that's quite accurate.
West coast jazz had a relatively short life span. Although the musicians lived on, West Coast was dead after 65, while the very same musicians evolved into other forms of jazz. The very best jazz from this genre would be in the 50's. This means that although you have the same West Coast musicians after the 50's, they may, or may not still be playing "West Coast" jazz.
Enjoy the music.