Accepted that the energy comes from both partners, 50% and 50%, to lead is not necessary being the one with the left arm open or the one who does "the leader's steps".I wonder whether there is already an established vocabulary/typology out there to distinguish among different types of hyper-active following. I add "hyper" because following is not a passive activity by default (I have experiences of dancing with totally passive followers who seem to expect me to even move their legs instead of them), but there are certain ways of interacting with the lead which noticeably deviate from the common thumb-rule of lead-follow separation in tango.
Leading, for me, basically means taking the initative and affecting in some way the movement, the position, and sometimes the balance of the other. Meanwhile, mantaining anyway a good connection and adapting to any reaction, even if it is different from what you expected.
From this point of view, the "lead backleading" is just a perfect case of leading, done by the one who is supposed to primarily follow, while the "step backleading" is a case of poor leading, almost dancing alone.
Moreover, the difference with "overtaking the lead" can be relevant only if we think in terms of "leader's steps" and "follower's steps", but is it really necessary?