The correct stroke
The adze is swung with the wrist, so this is also the pivot point of the tool. If you draw an arc around the centre of the wrist (marked by an x in the drawings) which runs along the top of the blade, this shows the curve in which the adze is swung (see figure 1 and 4).
The back of the adze that touches this curve is the support surface, similar to a plane. Figure 5 shows how an adze works that does not follow this radius, i.e. does not have a round back. This kind of adze cannot bite through wrist movement alone.
It must also be dragged (as when hoeing beds), which does not allow precise strokes and is not ergonomic. In addition, the adze is immediately driven out of the workpiece again because the elevation on the back acts as a kind of lever.
Figure 3 shows a trough-maker's adze that was made following this principle and works perfectly.
Using the blade
In the drawings, the radius is shown as a red line. Being the radius, this line is almost perpendicular to the back of the adze. So the full surface of the cutting edge meets the workpiece, similar to a plane blade.
In figures 2 and 5, the cutting edge does not fully align with this line. The adze in figure 2 thus penetrates the workpiece first with the sides of the curved blade. This makes it almost impossible to apply the adze with precision because you cannot work out when the tip will touch the workpiece. In figure 3, on the other hand, the tip of the adze touches the workpiece first, which makes it hard to apply the sides precisely.