I think we have to go back to basics;
SCA works on the approximate application of SIN / COS in a right angle triangle.
In the left diagram, A - B is parallel to C - D. The triangle formed by a line crossing the two lines will be a right angle triangle.
In the right diagram, the lines are not parallel. Just like in navigation where we are diverging from the planned track.
The triangle formed will not be a right angle triangle.
Thus SCA (which is based on a right angled triangle) will never work when the lines are diverging. It is a mathematical imposibility.
So are we asking the student to (as well as everything else) decide if the error is big or small?, going to leave us with a big or small (or even bigger than we started with) error after using SCA.
That is not KISS.