I can not speak to other vendors but all the Korean sticks currently in our store have Gersung which is the higher quality of the micros.
Most manufacturers offer different options on the sticks. IL does this with all their joysticks. Vendors can pick up cheaper parts, and still sell a name brand by using lower quality micros. It’s factory original, just the low end model.
curving actuators can help with direct actuation but it will also distort the diagonals. Increasing the actuator size is the easiest way to adjust for switches with low actuation points.
Zippy switches are in a few varieties. Just like every other company they offer many different models, at many different quality levels. Also like most other things, Zippy has been cloned by other Chinese companies. The company Zippy is actually a Taiwanese company, which tends to have better design controls and reliability than mainland China. Happ’s standard switch is specified as an E-switch or a Zippy now.
Zippy switches are not the default switch put on most cheap buttons from China, most wholesalers over there actually go one step further down the food chain and use a red and black or blue and black microswitch called King or some other name. Most Chinese buttons come from wholesalers with 125 gram micros installed. Playing with with those is a work out.
In regard to offering them as a product, most vendors selling to the mame or classic community offer Zippy or E-switch, which are about the same. Zippys and E-switch’s have become the standard micro for almost all Happ/IL style buttons now, whether from China or not. Cherry has made themselves almost unapproachable. We have tried to make deals with them but they insist on 10k minimum orders at over 1.50 per micro in that kind of bulk. This is sad because they don’t need to be restrictive in distribution and they are a better quality switch.
In regards to the silent nature, it is do to a lower operating force so the “snap” in the snap action switch is much quieter, hence silent. As a vendor I provide options that customers ask for, people asked for kits so I offered them, that is the nature of capitalism.