For this older post you could have hidden the lines but in reality the green lines are valid since you had a change in gradient across that surface (the trapeziums to the left and right are non-planar).
The level at the very top of the image is different to the level at the very bottom whilst the inner rectangle is at a constant level. The only way you could have legitimately removed these lines is if the bottom line in the image matched the level of that at the top or if the inner rectangle was sloping at same gradient and direction as outer rectangle.
They don't need the omitted lines to construct it (so they are unnecessary in that respect). It is non-ambiguous with or without the extra lines for this case but it is showing the reality of the planar surfaces you will end up with. Omission of such lines in other cases may create ambiguities. However if you set out the intersection points of the edges rather than placing a level somewhere along an edge it tends to deal with those such ambiguities that could arise.
