Not quite sure I'd agree with that statement Mark. Posters were "framed" in box's outside and in at Cinemas. We may not call them frames, display cases usually, but they do the same job. Display.
Like any piece of art/print/photo to go on walls around the home, frame choice has to be right for the individual living with it, so it is a very personal choice.
Personally I like wood, the ones in my poster room are matt black due to the other colours in there, but around the house we have a lot of mahogany, and walnut wood, so I go for mahogany frames with a gold inlay on the inside of frame. I hate large frames, so a subtle 1"-1 1/4" frame is all. I also hate to see a Matte, or surround inside inside the frame, there's no need...
I'd, like to see some pics of yours Mark if possible, you have me curious now...
The Saving Private Ryan would look best with a Matt Black frame as it would extend the black from the bottom to around the poster, so I'm sure you made the right choice. It will look quite the ticket.