All I can say is the Spanish re-worked and re-built their rifles over the years mixing and matching whatever parts fit and worked. I have a Polish WZ that had mostly Germanicon parts on it that worked great because I also got a German AZ that needed it's metal bands, etc. Polish parts are available, German ones weren't.

I don't think the swapping is deliberate, it's just a matter of a couple of rifles not working and combining the two to make a good one.