DFC - replying to your post at 11.56.
Your case A hasn't applied a correction. He should have realised that the error is a cumulative one and a correction to get back on track as well as the heading correction is applicable. He should fly 345 for 4 minutes then correct to 360.
Just like your case B has!
In all cases the SCA will get you back on track, but if it's a cululative error such as an incorrectly applied drift, that has error has to be corrected as well.
I doubt BEagle will say much different to me when he comes back on. He learned the SCA at the same place a me, we were on the same Squadron and later he was the CFI of the flying club I instructed at.