Whereas yellow gaterons have a variable spring coil, tighter on the outside and wider on the inside, resulting in a 'tactile' linear switch, you can feel the force required for actuation change through the depression.
This is what is called a progressive spring rate, all other momentary switch springs I know of from F BS, M BS, Alps, Space Invaders, Cherry, Kaliah, etc, are a linear spring rate. I am referring to the metal coil springs only. For example, lets increase the numbers to make it easier to understand and type. Lets say you have a spring with a 1 pound per inch spring rate. It takes 1 pound to depress the spring 1 inch, 2 pounds for 2 inches, and so on. On the progressive spring rates, 1.5 pound for the first inch, 3 pounds to get 2 inches, 4.5 pounds for 3 inches, etc. This can be accomplished a couple ways, but the easiest is by varying the distance between coils. The closer the coils, the lighter the spring rate. However, this comes at the cost of reduced travel. The one other cavet with this is to get a truely progressive spring rate, it requires constant changing of the coils per inch.
There are other patterns that spring makers can do to alter and shape the graph of the spring rate.