Polearms: Butting In

Watching this video of medieval fighting techniques and something interesting struck me.
In the polearm combats, notice how often the butt end of the weapon is advanced towards the enemy. Recently I was rereading one of the Black Medicine books and in that text the author recommends if defending yourself with an object such as a broom or long handled shovel to keep the head to the rear. I looked at some contemporary illustrations of combats with pole arms and there were numerous incidences of fighters having the butt towards the enemy. Many of these seemed to occur during what might be interpreted as defensive actions. If you consider a rifle when it is used for close combat, with or without the bayonet the butt is to the rear. However, the rifle butt is the primary striking element of the weapon so functionally the rifle butt serves the same role as a poleaxe head.
If we think about this, defending with the butt end of a pole arm makes quite a bit of sense. The butt end is lighter and therefore more mobile, quicker and more responsive. The heads of polearms sometimes bind together (as can be seen in the video clip), which may not be desirable. Deflecting the head with the butt reduces this. For example one could parry with the butt, riposte with a strike from the butt end and then follow-up with a strike from the head of your weapon.
Following this line of thought, I recalled something I had briefly scanned through recently. In a print out of a Di Grassi manual that used to be on line was the following passage:
“But because these weapons for the most part are exercised and used to enter through diverse Pikes and other weapons, and to break and disorder the battle array, to which end, and purpose, if it be used, then that manner of managing and handling is very convenient which is much practiced now a days, and thus it is. The Partisan, Halberd, and Bill (but not the Javelin, being in this case nothing effectual because it has small force in the edge) must be born in the middle of the staff, with the heel thereof before, and very low, and the point near a man’s head. And with the said heel, or half staff underneath, from the hand downwards, he must ward and beat off the points and thrusts of the Pikes and other weapons, and having made way, must enter with the increase of a pace of the hindfoot, and in the same instant, let fall his weapon as forcibly as he may, and strike with the edge athwart the Pikes. This kind of blow is so strong (being delivered as it ought, considering it comes from above downwards, and the weapon of itself is very heavy) that it will cut asunder not only Pikes, but also any other forcible impediment.”
In other words, hold your polearm near the middle, with the head back and defend with the lower part of the shaft until it is time to use the head. This position combines elements of both the high guard and the hanging guard. The rifle position with the butt back and the muzzle raised combines the middle guard and the tail guard. Middle guard and hanging guard are good defensive guards, while high and tail guard cock the weapon ready for a wide range of counterstrikes.
This blog post confirms the practice and suggests that on the shorter models of pole arm the fighter gripped closer to the head to preserve enough shaft to defend with.
This explains why many pole arms have always appeared too long or too heavy to me. In the movies halberds etc are always shown advancing point first, like overweight bayonets. Their heads looked too heavy to provide a quick defence and they had little room to generate power for chopping. In fact they were supposed to the held in the middle, head back.