Many of the images that I have found of MS with the 'set back' sight are in cases with British gunmaker's labels. I've guessed at it being a 'British thing' myself.

Here's a Westley Richards rifle with the 'set back' front sight.

On the other hand, though a Mannlicher Schoenauer with the factory take down system is often referred to as 'British Take Down', my M1910 take down has the sight at the muzzle. It is cased, but if there was ever a label it is long since gone. My grandfather bought it second hand in Ceylon ca. 1932.