-of course, what interests many XPS users are the components within a signal which are created by different chemical moieties with different chemical shifts, so the FWHM which you see in your material spectrum is the result of the peak being an envelope of multiple peaks with a smaller FWHM
Now, of course in a nanoparticle you will see shell and core atoms, although the contributions of the latter are limited by the electron escape path length, so you might say the envelope FWHM is affected by the structure, but recalculating to a particle size in the simple way you can use in XRD doesn't work.