While I agree that white label promos of later pressings are rare, they do exist. Here is one: Curtis Mayfield - Superfly The original album came out on Curtom in 1972. This WLP is from when the album was reissued by RSO in 1979, although I guess this would be considered the first RSO pressing.
Here are some additional Sinatra white label promos. I think these are all different from the ones in your pictures.
By and large the white labels are from initial runs. But plenty of exceptions exist. Jim Croce's Lifesong reissues being a perfect example. They come on white label promos too.