As others have said RA4 is all resin coated paper. Have you experienced all the surfaces available or are you basing your preception on what you imagine plastic to look/feel like? Ilford Satin is RC and yet has little ressemblance to what the "man in the street" woud assume to be a plastic finish. Likewise RA4 RC surfaces.
If you tell us what your issue with "plastic" is we might be able to be more helpful