Policies of triangulation and convex hull algorithms
The only 2d triangulation algorithm currently requires the points on a convex hull. The 3d algorithm constructs the convex hull first and does triangulation and convex hull in one step. Both are only some possible triangulation algorithms. Currently, the algorithms in all dimensions use different policies which suggest that things are more general than they are. On a close look, the current interface / policies doesn't seem to extend to more general cases and whether such will be needed at some is also unclear.
See also discussion in !2977 (merged)