Though I'm here in the heart of historical Common Purlin land, I've cut plenty of these over the years (one even right on the coast - Pancake head structural screws) and have always seen the advantage being the self defining geometry - (as opposed to simple bird's mouths) When the step goes home the whole of the rafter is where it belongs.

And I've never seen them as all that hard to cut, (85% of the waste in both the step and the lap is best removed with an ax) even when controlling and truing the geometry with datum based layout - Yes you can place these precisely in even the wonkiest full length plates.