I've been meaning to post a long discussion of the auxiliary's attitude for a while, so I took your post as my cue, but I've started a new thread on the subject.Did Myers ever provide reasoning for her decision to turn the auxiliary to the opposite direction of the dominant?
Myers largely rested her case on a sentence in Psychological Types where Jung says the auxiliary function is "in every respect different" from the dominant function. And I'd agree that her interpretation of that sentence would appear to be the best one if all you do is look at that one sentence in isolation. But the trouble is, that interpretation seems inconsistent with way too much else in Psychological Types.
And you'll find a little speculation by me as to Myers' possible motivation in the last spoiler of the linked post.