Does a cotton versus silk pillowcase really make a difference for wrinkles?
Based on the available study, nothing can be said about this. The source contains no information about pillowcases or wrinkles, so no conclusion can be drawn from it.
The available source contains no data whatsoever on pillowcases, cotton, silk or wrinkle formation. The provided study concerns heat transfer at a very small scale and body temperature regulation, and is therefore entirely unsuitable for answering this question.
Based on what is presented here, it cannot be said whether or not the material of your pillowcase has any effect on wrinkles. Quite simply, no source has been provided to support that.
To answer this question fairly, research would be needed that directly compares skin friction, sleeping position and differences in material. That is entirely absent here.