Here in the UK it was pretty common up to say the 1940s for plasterers to curve the corners on outward pointing walls in hallways. This usually extends from the skirting up to the picture rail. There is a lovely transition from the curve to a point just below the picture rail, which is very elegant, but a total pain if you are hanging wallpaper, well, that's my experience anyway!

I've always felt it was one of those details that a plasterer could show off their skill, and you are right, it softens the corner in a very pleasing way.