Mixed Tug movement

[Plantagenet]

I guess it must be in specific lists where there is any benefit to swapping the ranks around vs say a crusader mixed spear / crossbow formation which, unless I've misunderstood, would get no benefit whatsoever given the front rank of spears / crossbow shoot at full capacity as crossbows and fight at full capacity as spears depending on what they are doing. In this case it seems like the rear rank of crossbows is really only the unit marker so the mixed formation is visibly different to the non-mixed spear / crossbow units.