granted, at 11' in the air, that meant the destined target was 10-11' away, so being wide open was less of a risk at that range, than say much closer.
The target's actually probably notably closer than that. That height is *including the person* - so 4-5 feet of person, and then 5 to 6 feet of weapon - but you aren't pivoting the weapon and your body around your feet. So the target is probably no more than 6 feet away. That means if he takes *one* step forward, he's inside your reach.
That said, it works fine, *if* there's a sword-and-board guy between you and the target. Otherwise, having the weapon at full-extension like that leaves you vulnerable, as at full extension you don't have the lever-arm to change the direction of that head quickly. And, if he gets inside, you can block with the haft (after drawing it back in from that extension, anyway), but you can't *strike* with it, so unless you can gain distance again somehow, you are hosed.
We sparred a friend with boffers, who'd had some SCA big sword fighting training, and the technique was similar. Blade up, ready to do a rapid levering on the pommel. Packed quite a wallop. on the head.
When I fight in the SCA, I'm a polearm guy. When you're one-on-one, the better technique is to have the pommel near your shoulder or head, but the striking head maybe 11 *inches* from the ground, rather than feet - so the weapon is angled downwards - and your hands are shoulder-width or more apart on the weapon. Now, in order to reach you, they have to go around this big stick (you can block with the haft very effectively) and with the wide handgrip, you can change the direction of the weapon "wicked damn fast" as they say in New England. You have really good shots at the thigh, hip, and torso. Having your hands far apart gives you lots of leverage, and that means speed in this context. The drawback is, unlike with a sword-and board, you usually can't block and strike at the same time, as your shield and your weapon are the same object.
Alternatively, you have one hand near the butt of the weapon, somewhat behind you, the other hand up near the head - again, a very wide grip - with the head pointing toward the enemy at waist level. This is for spear-like thrusting. It works better if you have a sword and board partner, or a line of polearms/spears.
Techniques with large swords are different, as the weapon is shorter, and has more striking surface than haft. The gripping length is much shorter, so you have to keep your hands closer together.