Why is it not recommended to create a blend face that results in a point.
In those cases where blends cause the blend face to result in a point, could cause self intersection issues if the edges or curves are not trimmed properly, also it could be that some don't recommend having those cases because it could cause downstream application issues such as with CAM or CAE functions. Also suggest that the users Examine the Geometry if they need to have this condition in there models, just to be sure that they pass the Data Structure, Consistency, Self-Intersection, Face Intersection checks.