If the convertor hub is worn on one side it is likely that the hub / snout is not on centre to the convertor. If the hub is worn all the way around then there is an alignment problem between the crank centreline and the trans centreline and it needs to be addressed.
Your first statement is incorrect - your second statement is correct.
Think of it this way - a piece in the lathe being cut - if it is crooked, as you come in with your tool what happens ?
You cut only a portion of the part.
If it is perpendicular to the drive head you cut all the way around.
The crank is the drive head, the converter is the part being turned and the bushing is equivalent to the cutter.
