Now we are making progress here!

Eric, your intructor was stating his personal opinion re blocking because, as you noted, his definition is NOT in the GCR. And you can have that COA opinion bronzed but COA opinions are NOT binding precedent and any SOM or COA can come to a completely opposite conclusion. That is another pet peeve of mine - I think COA opinions should be precedential. That way, even w/o changing the GCR we end up with (more or less) consistent clarifications and applications over time.

The BMW explanation sounds exactly like what I surmised and stated above. However, again, The Runoffs SOM apparently decided that the overtaking car was NOT entitled to racing room and that the overtaken car was free to turn in early.

Although I had never seen them, the NASA passing rules are just what I had in mind. I'm sure those guys still argue about interpretations but those rules would seem to me to clear up a lot of the ambiguity and give the drivers pretty clear notice of what they can do and not do.