It is not completely so with wood that they cannot be press fit for assembly. To a degree they can but will or could be less precise and solid. In combination with adhesives and glue it can be very
good. This is so with different materials. Many of the Wenger metal scales you will see glue involved. Other SAKs got open rivets with pinned construction and this is a very sturdy method.
the history of pocket knives you will find scale materials soldered to the side-liners.
It is very typical for SAKs to have a serious precision. The Dynasty, Titanium, Porsche and
several others in history are examples. Pretty much all of the different scales had Swiss precision involved. Other very impressive SAKs are the EvoWood and RangerWood knives. These scales were made so well that they look custom made. Victorinox continued
these scales with some alterations. Still highly impressive knives.