The one time (MANY years ago) that I test-fitted a PPK slide to a PP frame, the slide fit right on, but was slightly looser, nor would it have surprised me if it had been a little tight.
Take into account that this was a test using a Walther 1960's PP and a 1960's PPK both made in Europe.
The results might be quite different with guns of different eras, and especially of different makes.