I can confirm that it is a Bug from logging in to the Alt and training new skill - that is exactly when I today got my 4th skill (slicing).
Not it's not just a 'graphical glych' - it also let's me send companions on that skill (0/400) missions - except they are call the same, look the same, are the same - as my other skill (Diplomacy), even give me Light vs. Dark points and last but not least - raise my Diplomacy skill (Slicing still 0/400).
So shows up at 4th skill, and missleads you into thinkging you are sending companion on that skill's missions.