Some of the best ulus are made by Knives of Alaska. Google the name. They're a very useful knife. Basically made from a ~60 deg section of a circle. The name of the Italian style chopper is a mezzluna for its crescent name. These are available from a number of manufacturers both in single and double blade configuration.
The mezzaluna is a specialty blade, useful for mincing and not much else. The ulu is another story. While it's an intuitive mincer, it's also a real generalist. A chef's knife or a "Chinese Chopper" from another culture. However, like either of these it takes learned skills to use it for most tasks. And like both, it is especially suited for preparing the cuisine it evolved with. Some people have mobility or hand problems which make these knives very worthwhile, for instance you can do a pretty good job of fine chopping while sitting at a table, or even with a board across the arms of a wheel chair.
For most of us though, neither is much better than "walking" the knife through," aka "two hand rock chop." I recommend either knife if you can afford the time and space for yet another specialty knife. Me, I just reach for the chef's when I start cooking. If you don't know the technique (which is not mine but pretty much universal), I'll be happy to explain. It's easy. Try it once or twice and you'll own it.
The technique Siduri describes is probably a form of rock-chopping. I've also heard rock-chopping described as "point down," if that helps. Rock chopping depends on the arc of the chef's knife blade near the point. The cook lifts the back of the blade, while the tip stays down on the board. The lift of the blade is controlled by the arc of the tip. Then the cook reverses the motion and the blade arcs down. The mechanics involve three fulcra ("virtual hinges" if you prefer) One, at the point of the knife, one at the cook's wrist, and the third at the cook's elbow. Actually, done right with a 'pinch grip," there's a fourth "virtual hinge" at the grip point. It sounds complicated, but isn't really that bad. It's a lot like pumping an old fashioned hand pump, or an old-fashioned car jack. It takes a home cook a couple of months of thinking about it before it finally becomes intuitive. Worth it.
The actual cutting action adds some shearing action to push-cut. The more rounded the belly of the blade, the more shearing. With a little practice, a cook can be very fast. Done one handed it won't mince as fast or as powerfully as done two handed -- because the second hand steadies the knife on its fulcrum. However for chopping tasks where consistent sizes and angles are important it's one of the two best ways to roll.
Perhaps Siduri meant a slightly different chopping technique used mostly with flatter blades uses fewer virtual hinges which mimics a "crack the whip" wrist motion. One essentially slaps the board with the knife. This is always done one handed, and is especially suited to the pinch grip. It's not as powerful as a rock chop but is very accurate, especially when the off hand holding the food is used in a "claw" position.
"Pinch" and "claw" are the foundations of good knife technique.