I have never seen Robertson screws on any factory gun that I remember.
Maybe it doesn't matter for the one who installs the wrong screws on a gun, they know what it is. Behind rubber ... out of sight, out of mind. You can't see it, so who cares. Well, I do when I round off the tip of my Phillips on that Robbie head 'cause I press hard so it doesn't slip.
If you can't see the screw in the pad, a Phillips will grab the Robbie head somewhat, but will slip on you.
I expect to find Phillips screws behind every buttpad with the exception of some earlier models before Phillips time. When I find Robertson screws as a replacement is when I cuss bubba. If there's a slot head, phillips won't catch, so I know I'm using the wrong screwdriver.
There's absolutely no reason for stripped screws if you know what you're doing. If you've been stripping screws, feel you need a Robbie replacement, park your tools and step away from the gun.
If a Robertson is such a great screw head, why are Phillips heads used for hanging sheetrock?
Don't get me wrong, I love the Robbie head, (it's Canadian, from Cobourg, Ontario), for building decks and screwing down floors, not on guns.
Oh, and use the thiner shaft Phillips screwdriver with some oil, so you don't stretch the rubber holes in the pad while you're at it.