there is no default way to do this and of course you are right. Modo Bake Curvature does not take any normal map or height map into account.
The way I do it is to:
1) Attach a 'Edge from Normal' Node (also Extension Pack) to your Normal Map Channel
2) Convert to Paintable / Bake to Paintable to get an 'edge mask' from your normal map
3) Blur the resulting map if necessary (because of pixelation, artifacts or whatever)
4) Screen the result over your curvature map
This should effectively give you what you are looking for.