Yes, really. Show me where it is OK to use a 3rd party vinyl/metal/plastic/platinum/unobtanium plate not issued by the DMV. Guess what, you can't. And before you go into the tangent 'oh, but there is a 3rd party company that does sell vinyl plates that are legal...blah blah blah.' Yes, those are
issued to you; that company had been approved and works with the DMV. So no, you can't use any 3rd party vinyl, or any other material, plate that is not issued by the DMV. Guess all that went over your head.
Have a cookie and relax.