You shouldn't come flying in on port unless you are absolutely certain of yourself.
You have that backwards. You shouldn't tack in front of an oncoming boat unless you can complete your tack and then give him room to keep clear.
I did not understand the rule then, and I doubt that anyone does.
Port tackers will now be completely out of control, using the fact of a collision to prove they were in the right.
I don't doubt this was a good rule at 6 knots...