Troops making spontaneous advance do not get to ignore TZ's, and the spono move "ends when it contacts friends it cannot pass thought" - after than it can still use the 80p to line up.
So as long as the directions of the advance were correct then the move seems legal to me
You are corect that the direction fo the advance cannot be altered to aim for a rear support - but getting into rear support will often be the result of a move straight ahead or towards the nearest enemy.