On these thoughts. If someone says "Don't do X.", then I am thinking so much about X, I'll end up doing it, when I might not have done so at all otherwise. In fact, that has happened to me with some teachers early on. Meanwhile, where I have poor habits, the number one thing I need to learn is how to do the good habit, and I can only start practising it when I do know what it is that I am to do, so that I can start doing it. I'm in massive remediation, so I have found out what things work, because I've been doing it for a while.
Some efforts may actually cause problems. If you try to keep your fingertips square, because you were told to do that, you might tense your hand in weird ways. If you're scared of hitting a black note that is not to be played, and stretch the non-playing finger way up, ahead of time, you can create tension in the hand. If you don't know you can angle your hand different ways. etc.
Meanwhile a thing somewhere else can cause a problem. Poor balance in the lower torso can cause a tense back can cause something wonky in the little finger: but because you're worried about the little finger, and no matter how much you fuss about it, nothing changes, because the problem is actually about shifting your weight on the bench. etc.
In his other question, the OP stated that he is mostly self-taught. We don't know what tools he has, and it might be good to see this teacher's own hand doing the same thing, in case we can get some clues from that.