Why shouldn't I use this sharpener on the "single-edged knives" mentioned in the description?

Ordinary household kitchen knives are ground evenly on both sides, but single-edged knives are made by beveling only one side of the blade. The cross-section is asymmetrical and only one side is sharpened, so they are used to slice ingredients thinly and cleanly.

The blade-sharpening mechanism is different. With this pull-through sharpener, when you insert the knife into the slot and pull, facing whetstones engage and sharpen both sides of the blade at once. It is a 2-stage sharpening method consisting of a diamond whetstone that first restores worn blades and an alumina-based ceramic whetstone that finishes the surface smoothly^[1]. Because it is designed to balance both sides, it cannot be used on single-edged knives that need only one side sharpened, or on ceramic knives that are vulnerable to friction impact^[2].

Generally, the correct maintenance method to preserve the original shape of a single-edged knife is to lay the knife flat on a flat bench whetstone and sharpen one side at a time with water while maintaining the angle.

hmmm: the easier a cooking tool is to use, the more essential it is to first check the cross-sectional shape of your knife to handle tools for a long time without ruining them.