These days it’s not just smaller frames that have steeper down tubes ie needing lower head lugs of a shallower angle. Almost all lugs are designed for road bikes with the clearances for 25mm tires - but most of what I’m building these days are “all-road” or modern road bikes, using clearances for 700x38 with fenders, or 700x42. So the lower head lugs need to be more like a 57-degree or 58- degree, and likewise the bottom bracket shell needs a shallower subtended angle, again more like 57 or 58 degrees vs the usual 60 or 61 degree angle between down tube and seat tube.

Fortunately, there are a few (but only a few) lugs and bottom brackets now becoming available with these numbers. Hopefully more as time goes on. As Andy says, I can sneak a degree on cast lugs without any blacksmithing.