I suspect that the high mounted sights are standardised for the new rifle as you can see in the photo of the unscoped rifle.
So, if you decide to mount the Mauser system scope on the action, you can still see the sights over them. A good idea but they just look tall on the unscoped rifle.
Looks to be very good quality too. I wonder, are we entering the era when a US custom gunmaker can't build you a rifle as well done as a new Rigby for the same price?